diff --git a/Cargo.lock b/Cargo.lock
index 602bfc261..2503176fe 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1923,6 +1923,7 @@ dependencies = [
  "eth2_ssz 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "eth2_ssz_derive 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "proto_array",
+ "state_processing",
  "store",
  "types",
 ]
diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index 5f8b70bf4..7a253e4e8 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -2838,6 +2838,11 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                     SyncAggregate::new()
                 }))
         };
+        // Closure to fetch a sync aggregate in cases where it is required.
+        let get_execution_payload = || -> Result<ExecutionPayload<_>, BlockProductionError> {
+            // TODO: actually get the payload from eth1 node..
+            Ok(ExecutionPayload::default())
+        };
 
         let inner_block = match state {
             BeaconState::Base(_) => BeaconBlock::Base(BeaconBlockBase {
@@ -2876,6 +2881,28 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                     },
                 })
             }
+            BeaconState::Merge(_) => {
+                let sync_aggregate = get_sync_aggregate()?;
+                let execution_payload = get_execution_payload()?;
+                BeaconBlock::Merge(BeaconBlockMerge {
+                    slot,
+                    proposer_index,
+                    parent_root,
+                    state_root: Hash256::zero(),
+                    body: BeaconBlockBodyMerge {
+                        randao_reveal,
+                        eth1_data,
+                        graffiti,
+                        proposer_slashings: proposer_slashings.into(),
+                        attester_slashings: attester_slashings.into(),
+                        attestations,
+                        deposits,
+                        voluntary_exits: voluntary_exits.into(),
+                        sync_aggregate,
+                        execution_payload,
+                    },
+                })
+            }
         };
 
         let block = SignedBeaconBlock::from_block(
diff --git a/beacon_node/beacon_chain/src/block_verification.rs b/beacon_node/beacon_chain/src/block_verification.rs
index 5ddeafa45..bf03cf979 100644
--- a/beacon_node/beacon_chain/src/block_verification.rs
+++ b/beacon_node/beacon_chain/src/block_verification.rs
@@ -48,7 +48,7 @@ use crate::{
         BLOCK_PROCESSING_CACHE_LOCK_TIMEOUT, MAXIMUM_GOSSIP_CLOCK_DISPARITY,
         VALIDATOR_PUBKEY_CACHE_LOCK_TIMEOUT,
     },
-    metrics, BeaconChain, BeaconChainError, BeaconChainTypes,
+    eth1_chain, metrics, BeaconChain, BeaconChainError, BeaconChainTypes,
 };
 use fork_choice::{ForkChoice, ForkChoiceStore};
 use parking_lot::RwLockReadGuard;
@@ -56,6 +56,7 @@ use proto_array::Block as ProtoBlock;
 use slog::{debug, error, Logger};
 use slot_clock::SlotClock;
 use ssz::Encode;
+use state_processing::per_block_processing::{is_execution_enabled, is_merge_complete};
 use state_processing::{
     block_signature_verifier::{BlockSignatureVerifier, Error as BlockSignatureVerifierError},
     per_block_processing, per_slot_processing,
@@ -68,9 +69,9 @@ use std::io::Write;
 use store::{Error as DBError, HotColdDB, HotStateSummary, KeyValueStore, StoreOp};
 use tree_hash::TreeHash;
 use types::{
-    BeaconBlockRef, BeaconState, BeaconStateError, ChainSpec, CloneConfig, Epoch, EthSpec, Hash256,
-    InconsistentFork, PublicKey, PublicKeyBytes, RelativeEpoch, SignedBeaconBlock,
-    SignedBeaconBlockHeader, Slot,
+    BeaconBlockRef, BeaconState, BeaconStateError, ChainSpec, CloneConfig, Epoch, EthSpec,
+    ExecutionPayload, Hash256, InconsistentFork, PublicKey, PublicKeyBytes, RelativeEpoch,
+    SignedBeaconBlock, SignedBeaconBlockHeader, Slot,
 };
 
 /// Maximum block slot number. Block with slots bigger than this constant will NOT be processed.
@@ -223,6 +224,66 @@ pub enum BlockError<T: EthSpec> {
     ///
     /// The block is invalid and the peer is faulty.
     InconsistentFork(InconsistentFork),
+    /// There was an error while validating the ExecutionPayload
+    ///
+    /// ## Peer scoring
+    ///
+    /// See `ExecutionPayloadError` for scoring information
+    ExecutionPayloadError(ExecutionPayloadError),
+}
+
+/// Returned when block validation failed due to some issue verifying
+/// the execution payload.
+#[derive(Debug)]
+pub enum ExecutionPayloadError {
+    /// There's no eth1 connection (mandatory after merge)
+    ///
+    /// ## Peer scoring
+    ///
+    /// As this is our fault, do not penalize the peer
+    NoEth1Connection,
+    /// Error occurred during engine_executePayload
+    ///
+    /// ## Peer scoring
+    ///
+    /// Some issue with our configuration, do not penalize peer
+    Eth1VerificationError(eth1_chain::Error),
+    /// The execution engine returned INVALID for the payload
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    RejectedByExecutionEngine,
+    /// The execution payload is empty when is shouldn't be
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    PayloadEmpty,
+    /// The execution payload timestamp does not match the slot
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    InvalidPayloadTimestamp,
+    /// The gas used in the block exceeds the gas limit
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    GasUsedExceedsLimit,
+    /// The payload block hash equals the parent hash
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    BlockHashEqualsParentHash,
+    /// The execution payload transaction list data exceeds size limits
+    ///
+    /// ## Peer scoring
+    ///
+    /// The block is invalid and the peer is faulty
+    TransactionDataExceedsSizeLimit,
 }
 
 impl<T: EthSpec> std::fmt::Display for BlockError<T> {
@@ -668,6 +729,18 @@ impl<T: BeaconChainTypes> GossipVerifiedBlock<T> {
             });
         }
 
+        // TODO: avoid this by adding field to fork-choice to determine if merge-block has been imported
+        let (parent, block) = if let Some(snapshot) = parent {
+            (Some(snapshot), block)
+        } else {
+            let (snapshot, block) = load_parent(block, chain)?;
+            (Some(snapshot), block)
+        };
+        let state = &parent.as_ref().unwrap().pre_state;
+
+        // validate the block's execution_payload
+        validate_execution_payload(block.message(), state)?;
+
         Ok(Self {
             block,
             block_root,
@@ -989,6 +1062,34 @@ impl<'a, T: BeaconChainTypes> FullyVerifiedBlock<'a, T> {
             }
         }
 
+        // This is the soonest we can run these checks as they must be called AFTER per_slot_processing
+        if is_execution_enabled(&state, block.message().body()) {
+            let eth1_chain = chain
+                .eth1_chain
+                .as_ref()
+                .ok_or(BlockError::ExecutionPayloadError(
+                    ExecutionPayloadError::NoEth1Connection,
+                ))?;
+
+            if !eth1_chain
+                .on_payload(block.message().body().execution_payload().ok_or(
+                    BlockError::InconsistentFork(InconsistentFork {
+                        fork_at_slot: eth2::types::ForkName::Merge,
+                        object_fork: block.message().body().fork_name(),
+                    }),
+                )?)
+                .map_err(|e| {
+                    BlockError::ExecutionPayloadError(ExecutionPayloadError::Eth1VerificationError(
+                        e,
+                    ))
+                })?
+            {
+                return Err(BlockError::ExecutionPayloadError(
+                    ExecutionPayloadError::RejectedByExecutionEngine,
+                ));
+            }
+        }
+
         // If the block is sufficiently recent, notify the validator monitor.
         if let Some(slot) = chain.slot_clock.now() {
             let epoch = slot.epoch(T::EthSpec::slots_per_epoch());
@@ -1097,6 +1198,38 @@ impl<'a, T: BeaconChainTypes> FullyVerifiedBlock<'a, T> {
     }
 }
 
+/// Validate the gossip block's execution_payload according to the checks described here:
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/p2p-interface.md#beacon_block
+fn validate_execution_payload<E: EthSpec>(
+    block: BeaconBlockRef<'_, E>,
+    state: &BeaconState<E>,
+) -> Result<(), BlockError<E>> {
+    if !is_execution_enabled(state, block.body()) {
+        return Ok(());
+    }
+    let execution_payload = block
+        .body()
+        .execution_payload()
+        // TODO: this really should never error so maybe
+        //       we should make this simpler..
+        .ok_or(BlockError::InconsistentFork(InconsistentFork {
+            fork_at_slot: eth2::types::ForkName::Merge,
+            object_fork: block.body().fork_name(),
+        }))?;
+
+    if is_merge_complete(state) {
+        if *execution_payload == <ExecutionPayload<E>>::default() {
+            return Err(BlockError::ExecutionPayloadError(
+                ExecutionPayloadError::PayloadEmpty,
+            ));
+        }
+    }
+
+    // TODO: finish these
+
+    Ok(())
+}
+
 /// Check that the count of skip slots between the block and its parent does not exceed our maximum
 /// value.
 ///
diff --git a/beacon_node/beacon_chain/src/eth1_chain.rs b/beacon_node/beacon_chain/src/eth1_chain.rs
index aa6978b79..ec046b685 100644
--- a/beacon_node/beacon_chain/src/eth1_chain.rs
+++ b/beacon_node/beacon_chain/src/eth1_chain.rs
@@ -15,8 +15,8 @@ use std::time::{SystemTime, UNIX_EPOCH};
 use store::{DBColumn, Error as StoreError, StoreItem};
 use task_executor::TaskExecutor;
 use types::{
-    BeaconState, BeaconStateError, ChainSpec, Deposit, Eth1Data, EthSpec, Hash256, Slot, Unsigned,
-    DEPOSIT_TREE_DEPTH,
+    BeaconState, BeaconStateError, ChainSpec, Deposit, Eth1Data, EthSpec, ExecutionPayload,
+    Hash256, Slot, Unsigned, DEPOSIT_TREE_DEPTH,
 };
 
 type BlockNumber = u64;
@@ -53,6 +53,8 @@ pub enum Error {
     UnknownPreviousEth1BlockHash,
     /// An arithmetic error occurred.
     ArithError(safe_arith::ArithError),
+    /// Unable to execute payload
+    UnableToExecutePayload(String),
 }
 
 impl From<safe_arith::ArithError> for Error {
@@ -274,6 +276,15 @@ where
         )
     }
 
+    pub fn on_payload(&self, execution_payload: &ExecutionPayload<E>) -> Result<bool, Error> {
+        if self.use_dummy_backend {
+            let dummy_backend: DummyEth1ChainBackend<E> = DummyEth1ChainBackend::default();
+            dummy_backend.on_payload(execution_payload)
+        } else {
+            self.backend.on_payload(execution_payload)
+        }
+    }
+
     /// Instantiate `Eth1Chain` from a persisted `SszEth1`.
     ///
     /// The `Eth1Chain` will have the same caches as the persisted `SszEth1`.
@@ -334,6 +345,9 @@ pub trait Eth1ChainBackend<T: EthSpec>: Sized + Send + Sync {
     /// an idea of how up-to-date the remote eth1 node is.
     fn head_block(&self) -> Option<Eth1Block>;
 
+    /// Verifies the execution payload
+    fn on_payload(&self, execution_payload: &ExecutionPayload<T>) -> Result<bool, Error>;
+
     /// Encode the `Eth1ChainBackend` instance to bytes.
     fn as_bytes(&self) -> Vec<u8>;
 
@@ -388,6 +402,10 @@ impl<T: EthSpec> Eth1ChainBackend<T> for DummyEth1ChainBackend<T> {
         None
     }
 
+    fn on_payload(&self, _execution_payload: &ExecutionPayload<T>) -> Result<bool, Error> {
+        Ok(true)
+    }
+
     /// Return empty Vec<u8> for dummy backend.
     fn as_bytes(&self) -> Vec<u8> {
         Vec::new()
@@ -556,6 +574,15 @@ impl<T: EthSpec> Eth1ChainBackend<T> for CachingEth1Backend<T> {
         self.core.head_block()
     }
 
+    fn on_payload(&self, execution_payload: &ExecutionPayload<T>) -> Result<bool, Error> {
+        futures::executor::block_on(async move {
+            self.core
+                .on_payload(execution_payload.clone())
+                .await
+                .map_err(|e| Error::UnableToExecutePayload(format!("{:?}", e)))
+        })
+    }
+
     /// Return encoded byte representation of the block and deposit caches.
     fn as_bytes(&self) -> Vec<u8> {
         self.core.as_bytes()
diff --git a/beacon_node/beacon_chain/src/lib.rs b/beacon_node/beacon_chain/src/lib.rs
index 2cd636f23..19c366572 100644
--- a/beacon_node/beacon_chain/src/lib.rs
+++ b/beacon_node/beacon_chain/src/lib.rs
@@ -44,7 +44,7 @@ pub use self::errors::{BeaconChainError, BlockProductionError};
 pub use self::historical_blocks::HistoricalBlockError;
 pub use attestation_verification::Error as AttestationError;
 pub use beacon_fork_choice_store::{BeaconForkChoiceStore, Error as ForkChoiceStoreError};
-pub use block_verification::{BlockError, GossipVerifiedBlock};
+pub use block_verification::{BlockError, ExecutionPayloadError, GossipVerifiedBlock};
 pub use eth1_chain::{Eth1Chain, Eth1ChainBackend};
 pub use events::ServerSentEventHandler;
 pub use metrics::scrape_for_metrics;
diff --git a/beacon_node/eth1/src/http.rs b/beacon_node/eth1/src/http.rs
index 9e3465f0f..489142377 100644
--- a/beacon_node/eth1/src/http.rs
+++ b/beacon_node/eth1/src/http.rs
@@ -19,7 +19,7 @@ use std::fmt;
 use std::ops::Range;
 use std::str::FromStr;
 use std::time::Duration;
-use types::Hash256;
+use types::{Hash256, PowBlock, Uint256};
 
 /// `keccak("DepositEvent(bytes,bytes,bytes,bytes,bytes)")`
 pub const DEPOSIT_EVENT_TOPIC: &str =
@@ -49,6 +49,7 @@ pub enum Eth1Id {
 #[derive(Clone, Copy)]
 pub enum BlockQuery {
     Number(u64),
+    Hash(Hash256),
     Latest,
 }
 
@@ -135,13 +136,6 @@ pub async fn get_chain_id(endpoint: &SensitiveUrl, timeout: Duration) -> Result<
     }
 }
 
-#[derive(Debug, PartialEq, Clone)]
-pub struct Block {
-    pub hash: Hash256,
-    pub timestamp: u64,
-    pub number: u64,
-}
-
 /// Returns the current block number.
 ///
 /// Uses HTTP JSON RPC at `endpoint`. E.g., `http://localhost:8545`.
@@ -156,40 +150,74 @@ pub async fn get_block_number(endpoint: &SensitiveUrl, timeout: Duration) -> Res
     .map_err(|e| format!("Failed to get block number: {}", e))
 }
 
-/// Gets a block hash by block number.
+/// Gets a block by hash or block number.
 ///
 /// Uses HTTP JSON RPC at `endpoint`. E.g., `http://localhost:8545`.
 pub async fn get_block(
     endpoint: &SensitiveUrl,
     query: BlockQuery,
     timeout: Duration,
-) -> Result<Block, String> {
+) -> Result<PowBlock, String> {
     let query_param = match query {
         BlockQuery::Number(block_number) => format!("0x{:x}", block_number),
+        BlockQuery::Hash(hash) => format!("{:?}", hash), // debug formatting ensures output not truncated
         BlockQuery::Latest => "latest".to_string(),
     };
+    let rpc_method = match query {
+        BlockQuery::Number(_) | BlockQuery::Latest => "eth_getBlockByNumber",
+        BlockQuery::Hash(_) => "eth_getBlockByHash",
+    };
     let params = json!([
         query_param,
         false // do not return full tx objects.
     ]);
 
-    let response_body = send_rpc_request(endpoint, "eth_getBlockByNumber", params, timeout).await?;
+    let response_body = send_rpc_request(endpoint, rpc_method, params, timeout).await?;
     let response = response_result_or_error(&response_body)
-        .map_err(|e| format!("eth_getBlockByNumber failed: {}", e))?;
+        .map_err(|e| format!("{} failed: {}", rpc_method, e))?;
 
-    let hash: Vec<u8> = hex_to_bytes(
+    let block_hash: Vec<u8> = hex_to_bytes(
         response
             .get("hash")
             .ok_or("No hash for block")?
             .as_str()
             .ok_or("Block hash was not string")?,
     )?;
-    let hash: Hash256 = if hash.len() == 32 {
-        Hash256::from_slice(&hash)
+    let block_hash: Hash256 = if block_hash.len() == 32 {
+        Hash256::from_slice(&block_hash)
     } else {
-        return Err(format!("Block has was not 32 bytes: {:?}", hash));
+        return Err(format!("Block hash was not 32 bytes: {:?}", block_hash));
     };
 
+    let parent_hash: Vec<u8> = hex_to_bytes(
+        response
+            .get("parentHash")
+            .ok_or("No parent hash for block")?
+            .as_str()
+            .ok_or("Parent hash was not string")?,
+    )?;
+    let parent_hash: Hash256 = if parent_hash.len() == 32 {
+        Hash256::from_slice(&parent_hash)
+    } else {
+        return Err(format!("parent hash was not 32 bytes: {:?}", parent_hash));
+    };
+
+    let total_difficulty_str = response
+        .get("totalDifficulty")
+        .ok_or("No total difficulty for block")?
+        .as_str()
+        .ok_or("Total difficulty was not a string")?;
+    let total_difficulty = Uint256::from_str(total_difficulty_str)
+        .map_err(|e| format!("total_difficulty from_str {:?}", e))?;
+
+    let difficulty_str = response
+        .get("difficulty")
+        .ok_or("No difficulty for block")?
+        .as_str()
+        .ok_or("Difficulty was not a string")?;
+    let difficulty =
+        Uint256::from_str(difficulty_str).map_err(|e| format!("difficulty from_str {:?}", e))?;
+
     let timestamp = hex_to_u64_be(
         response
             .get("timestamp")
@@ -198,7 +226,7 @@ pub async fn get_block(
             .ok_or("Block timestamp was not string")?,
     )?;
 
-    let number = hex_to_u64_be(
+    let block_number = hex_to_u64_be(
         response
             .get("number")
             .ok_or("No number for block")?
@@ -206,14 +234,20 @@ pub async fn get_block(
             .ok_or("Block number was not string")?,
     )?;
 
-    if number <= usize::max_value() as u64 {
-        Ok(Block {
-            hash,
+    if block_number <= usize::max_value() as u64 {
+        Ok(PowBlock {
+            block_hash,
+            parent_hash,
+            total_difficulty,
+            difficulty,
             timestamp,
-            number,
+            block_number,
         })
     } else {
-        Err(format!("Block number {} is larger than a usize", number))
+        Err(format!(
+            "Block number {} is larger than a usize",
+            block_number
+        ))
     }
     .map_err(|e| format!("Failed to get block number: {}", e))
 }
diff --git a/beacon_node/eth1/src/service.rs b/beacon_node/eth1/src/service.rs
index 460f53e73..ca6e0c588 100644
--- a/beacon_node/eth1/src/service.rs
+++ b/beacon_node/eth1/src/service.rs
@@ -21,7 +21,7 @@ use std::sync::Arc;
 use std::time::{SystemTime, UNIX_EPOCH};
 use tokio::sync::RwLock as TRwLock;
 use tokio::time::{interval_at, Duration, Instant};
-use types::{ChainSpec, EthSpec, Unsigned};
+use types::{ChainSpec, EthSpec, ExecutionPayload, Unsigned};
 
 /// Indicates the default eth1 network id we use for the deposit contract.
 pub const DEFAULT_NETWORK_ID: Eth1Id = Eth1Id::Goerli;
@@ -331,6 +331,8 @@ pub enum SingleEndpointError {
     GetDepositCountFailed(String),
     /// Failed to read the deposit contract root from the eth1 node.
     GetDepositLogsFailed(String),
+    /// Failed to run engine_ExecutePayload
+    EngineExecutePayloadFailed,
 }
 
 #[derive(Debug, PartialEq)]
@@ -669,6 +671,21 @@ impl Service {
         }
     }
 
+    /// This is were we call out to engine_executePayload to determine if payload is valid
+    pub async fn on_payload<T: EthSpec>(
+        &self,
+        _execution_payload: ExecutionPayload<T>,
+    ) -> Result<bool, Error> {
+        let endpoints = self.init_endpoints();
+
+        // TODO: call engine_executePayload and figure out how backup endpoint works..
+        endpoints
+            .first_success(|_e| async move { Ok(true) })
+            .await
+            .map(|(res, _)| res)
+            .map_err(Error::FallbackError)
+    }
+
     /// Update the deposit and block cache, returning an error if either fail.
     ///
     /// ## Returns
@@ -1242,7 +1259,7 @@ async fn download_eth1_block(
     });
 
     // Performs a `get_blockByNumber` call to an eth1 node.
-    let http_block = get_block(
+    let pow_block = get_block(
         endpoint,
         block_number_opt
             .map(BlockQuery::Number)
@@ -1253,9 +1270,9 @@ async fn download_eth1_block(
     .await?;
 
     Ok(Eth1Block {
-        hash: http_block.hash,
-        number: http_block.number,
-        timestamp: http_block.timestamp,
+        hash: pow_block.block_hash,
+        number: pow_block.block_number,
+        timestamp: pow_block.timestamp,
         deposit_root,
         deposit_count,
     })
diff --git a/beacon_node/eth1/tests/test.rs b/beacon_node/eth1/tests/test.rs
index bb00ebaab..4141f8b78 100644
--- a/beacon_node/eth1/tests/test.rs
+++ b/beacon_node/eth1/tests/test.rs
@@ -1,6 +1,6 @@
 #![cfg(test)]
 use environment::{Environment, EnvironmentBuilder};
-use eth1::http::{get_deposit_count, get_deposit_logs_in_range, get_deposit_root, Block, Log};
+use eth1::http::{get_deposit_count, get_deposit_logs_in_range, get_deposit_root, Log};
 use eth1::{Config, Service};
 use eth1::{DepositCache, DEFAULT_CHAIN_ID, DEFAULT_NETWORK_ID};
 use eth1_test_rig::GanacheEth1Instance;
@@ -571,8 +571,9 @@ mod deposit_tree {
 mod http {
     use super::*;
     use eth1::http::BlockQuery;
+    use types::PowBlock;
 
-    async fn get_block(eth1: &GanacheEth1Instance, block_number: u64) -> Block {
+    async fn get_block(eth1: &GanacheEth1Instance, block_number: u64) -> PowBlock {
         eth1::http::get_block(
             &SensitiveUrl::parse(eth1.endpoint().as_str()).unwrap(),
             BlockQuery::Number(block_number),
@@ -639,7 +640,7 @@ mod http {
                 // Check the block hash.
                 let new_block = get_block(&eth1, block_number).await;
                 assert_ne!(
-                    new_block.hash, old_block.hash,
+                    new_block.block_hash, old_block.block_hash,
                     "block hash should change with each deposit"
                 );
 
@@ -661,7 +662,7 @@ mod http {
                 // Check to ensure the block root is changing
                 assert_ne!(
                     new_root,
-                    Some(new_block.hash),
+                    Some(new_block.block_hash),
                     "the deposit root should be different to the block hash"
                 );
             }
diff --git a/beacon_node/lighthouse_network/src/config.rs b/beacon_node/lighthouse_network/src/config.rs
index e18fd00ae..4ea3fa4b6 100644
--- a/beacon_node/lighthouse_network/src/config.rs
+++ b/beacon_node/lighthouse_network/src/config.rs
@@ -209,7 +209,9 @@ pub fn gossipsub_config(fork_context: Arc<ForkContext>) -> GossipsubConfig {
     ) -> Vec<u8> {
         let topic_bytes = message.topic.as_str().as_bytes();
         match fork_context.current_fork() {
-            ForkName::Altair => {
+            // according to: https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/p2p-interface.md#the-gossip-domain-gossipsub
+            // the derivation of the message-id remains the same in the merge
+            ForkName::Altair | ForkName::Merge => {
                 let topic_len_bytes = topic_bytes.len().to_le_bytes();
                 let mut vec = Vec::with_capacity(
                     prefix.len() + topic_len_bytes.len() + topic_bytes.len() + message.data.len(),
diff --git a/beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs b/beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs
index 6c6f0b9bc..c9db51406 100644
--- a/beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs
+++ b/beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs
@@ -17,7 +17,7 @@ use std::sync::Arc;
 use tokio_util::codec::{Decoder, Encoder};
 use types::{
     EthSpec, ForkContext, ForkName, SignedBeaconBlock, SignedBeaconBlockAltair,
-    SignedBeaconBlockBase,
+    SignedBeaconBlockBase, SignedBeaconBlockMerge,
 };
 use unsigned_varint::codec::Uvi;
 
@@ -375,7 +375,7 @@ fn handle_error<T>(
 }
 
 /// Returns `Some(context_bytes)` for encoding RPC responses that require context bytes.
-/// Returns `None` when context bytes are not required.  
+/// Returns `None` when context bytes are not required.
 fn context_bytes<T: EthSpec>(
     protocol: &ProtocolId,
     fork_context: &ForkContext,
@@ -383,23 +383,25 @@ fn context_bytes<T: EthSpec>(
 ) -> Option<[u8; CONTEXT_BYTES_LEN]> {
     // Add the context bytes if required
     if protocol.has_context_bytes() {
-        if let RPCCodedResponse::Success(RPCResponse::BlocksByRange(res)) = resp {
-            if let SignedBeaconBlock::Altair { .. } = **res {
-                // Altair context being `None` implies that "altair never happened".
-                // This code should be unreachable if altair is disabled since only Version::V1 would be valid in that case.
-                return fork_context.to_context_bytes(ForkName::Altair);
-            } else if let SignedBeaconBlock::Base { .. } = **res {
-                return Some(fork_context.genesis_context_bytes());
-            }
-        }
-
-        if let RPCCodedResponse::Success(RPCResponse::BlocksByRoot(res)) = resp {
-            if let SignedBeaconBlock::Altair { .. } = **res {
-                // Altair context being `None` implies that "altair never happened".
-                // This code should be unreachable if altair is disabled since only Version::V1 would be valid in that case.
-                return fork_context.to_context_bytes(ForkName::Altair);
-            } else if let SignedBeaconBlock::Base { .. } = **res {
-                return Some(fork_context.genesis_context_bytes());
+        if let RPCCodedResponse::Success(rpc_variant) = resp {
+            if let RPCResponse::BlocksByRange(ref_box_block)
+            | RPCResponse::BlocksByRoot(ref_box_block) = rpc_variant
+            {
+                return match **ref_box_block {
+                    // NOTE: If you are adding another fork type here, be sure to modify the
+                    //       `fork_context.to_context_bytes()` function to support it as well!
+                    SignedBeaconBlock::Merge { .. } => {
+                        // TODO: check this
+                        // Merge context being `None` implies that "merge never happened".
+                        fork_context.to_context_bytes(ForkName::Merge)
+                    }
+                    SignedBeaconBlock::Altair { .. } => {
+                        // Altair context being `None` implies that "altair never happened".
+                        // This code should be unreachable if altair is disabled since only Version::V1 would be valid in that case.
+                        fork_context.to_context_bytes(ForkName::Altair)
+                    }
+                    SignedBeaconBlock::Base { .. } => Some(fork_context.genesis_context_bytes()),
+                };
             }
         }
     }
@@ -559,6 +561,12 @@ fn handle_v2_response<T: EthSpec>(
                 ForkName::Base => Ok(Some(RPCResponse::BlocksByRange(Box::new(
                     SignedBeaconBlock::Base(SignedBeaconBlockBase::from_ssz_bytes(decoded_buffer)?),
                 )))),
+                // TODO: check this (though it seems okay)
+                ForkName::Merge => Ok(Some(RPCResponse::BlocksByRange(Box::new(
+                    SignedBeaconBlock::Merge(SignedBeaconBlockMerge::from_ssz_bytes(
+                        decoded_buffer,
+                    )?),
+                )))),
             },
             Protocol::BlocksByRoot => match fork_name {
                 ForkName::Altair => Ok(Some(RPCResponse::BlocksByRoot(Box::new(
@@ -569,6 +577,12 @@ fn handle_v2_response<T: EthSpec>(
                 ForkName::Base => Ok(Some(RPCResponse::BlocksByRoot(Box::new(
                     SignedBeaconBlock::Base(SignedBeaconBlockBase::from_ssz_bytes(decoded_buffer)?),
                 )))),
+                // TODO: check this (though it seems right)
+                ForkName::Merge => Ok(Some(RPCResponse::BlocksByRoot(Box::new(
+                    SignedBeaconBlock::Merge(SignedBeaconBlockMerge::from_ssz_bytes(
+                        decoded_buffer,
+                    )?),
+                )))),
             },
             _ => Err(RPCError::ErrorResponse(
                 RPCResponseErrorCode::InvalidRequest,
diff --git a/beacon_node/lighthouse_network/src/rpc/protocol.rs b/beacon_node/lighthouse_network/src/rpc/protocol.rs
index c00b9c049..0a711257b 100644
--- a/beacon_node/lighthouse_network/src/rpc/protocol.rs
+++ b/beacon_node/lighthouse_network/src/rpc/protocol.rs
@@ -21,8 +21,8 @@ use tokio_util::{
     compat::{Compat, FuturesAsyncReadCompatExt},
 };
 use types::{
-    BeaconBlock, BeaconBlockAltair, BeaconBlockBase, EthSpec, ForkContext, Hash256, MainnetEthSpec,
-    Signature, SignedBeaconBlock,
+    BeaconBlock, BeaconBlockAltair, BeaconBlockBase, BeaconBlockMerge, EthSpec, ForkContext,
+    Hash256, MainnetEthSpec, Signature, SignedBeaconBlock,
 };
 
 lazy_static! {
@@ -53,6 +53,20 @@ lazy_static! {
     )
     .as_ssz_bytes()
     .len();
+
+    pub static ref SIGNED_BEACON_BLOCK_MERGE_MIN: usize = SignedBeaconBlock::<MainnetEthSpec>::from_block(
+        BeaconBlock::Merge(BeaconBlockMerge::<MainnetEthSpec>::empty(&MainnetEthSpec::default_spec())),
+        Signature::empty(),
+    )
+    .as_ssz_bytes()
+    .len();
+    pub static ref SIGNED_BEACON_BLOCK_MERGE_MAX: usize = SignedBeaconBlock::<MainnetEthSpec>::from_block(
+        BeaconBlock::Merge(BeaconBlockMerge::full(&MainnetEthSpec::default_spec())),
+        Signature::empty(),
+    )
+    .as_ssz_bytes()
+    .len();
+
     pub static ref BLOCKS_BY_ROOT_REQUEST_MIN: usize =
         VariableList::<Hash256, MaxRequestBlocks>::from(Vec::<Hash256>::new())
     .as_ssz_bytes()
@@ -253,12 +267,18 @@ impl ProtocolId {
             Protocol::Goodbye => RpcLimits::new(0, 0), // Goodbye request has no response
             Protocol::BlocksByRange => RpcLimits::new(
                 std::cmp::min(
-                    *SIGNED_BEACON_BLOCK_ALTAIR_MIN,
-                    *SIGNED_BEACON_BLOCK_BASE_MIN,
+                    std::cmp::min(
+                        *SIGNED_BEACON_BLOCK_ALTAIR_MIN,
+                        *SIGNED_BEACON_BLOCK_BASE_MIN,
+                    ),
+                    *SIGNED_BEACON_BLOCK_MERGE_MIN,
                 ),
                 std::cmp::max(
-                    *SIGNED_BEACON_BLOCK_ALTAIR_MAX,
-                    *SIGNED_BEACON_BLOCK_BASE_MAX,
+                    std::cmp::max(
+                        *SIGNED_BEACON_BLOCK_ALTAIR_MAX,
+                        *SIGNED_BEACON_BLOCK_BASE_MAX,
+                    ),
+                    *SIGNED_BEACON_BLOCK_MERGE_MAX,
                 ),
             ),
             Protocol::BlocksByRoot => RpcLimits::new(
diff --git a/beacon_node/lighthouse_network/src/types/pubsub.rs b/beacon_node/lighthouse_network/src/types/pubsub.rs
index 75ef6e8ab..af2656a27 100644
--- a/beacon_node/lighthouse_network/src/types/pubsub.rs
+++ b/beacon_node/lighthouse_network/src/types/pubsub.rs
@@ -10,7 +10,8 @@ use std::io::{Error, ErrorKind};
 use types::{
     Attestation, AttesterSlashing, EthSpec, ForkContext, ForkName, ProposerSlashing,
     SignedAggregateAndProof, SignedBeaconBlock, SignedBeaconBlockAltair, SignedBeaconBlockBase,
-    SignedContributionAndProof, SignedVoluntaryExit, SubnetId, SyncCommitteeMessage, SyncSubnetId,
+    SignedBeaconBlockMerge, SignedContributionAndProof, SignedVoluntaryExit, SubnetId,
+    SyncCommitteeMessage, SyncSubnetId,
 };
 
 #[derive(Debug, Clone, PartialEq)]
@@ -161,6 +162,10 @@ impl<T: EthSpec> PubsubMessage<T> {
                                     SignedBeaconBlockAltair::from_ssz_bytes(data)
                                         .map_err(|e| format!("{:?}", e))?,
                                 ),
+                                Some(ForkName::Merge) => SignedBeaconBlock::<T>::Merge(
+                                    SignedBeaconBlockMerge::from_ssz_bytes(data)
+                                        .map_err(|e| format!("{:?}", e))?,
+                                ),
                                 None => {
                                     return Err(format!(
                                         "Unknown gossipsub fork digest: {:?}",
diff --git a/beacon_node/network/src/beacon_processor/worker/gossip_methods.rs b/beacon_node/network/src/beacon_processor/worker/gossip_methods.rs
index 2e5ee5160..dd42531cf 100644
--- a/beacon_node/network/src/beacon_processor/worker/gossip_methods.rs
+++ b/beacon_node/network/src/beacon_processor/worker/gossip_methods.rs
@@ -5,7 +5,8 @@ use beacon_chain::{
     observed_operations::ObservationOutcome,
     sync_committee_verification::Error as SyncCommitteeError,
     validator_monitor::get_block_delay_ms,
-    BeaconChainError, BeaconChainTypes, BlockError, ForkChoiceError, GossipVerifiedBlock,
+    BeaconChainError, BeaconChainTypes, BlockError, ExecutionPayloadError, ForkChoiceError,
+    GossipVerifiedBlock,
 };
 use lighthouse_network::{Client, MessageAcceptance, MessageId, PeerAction, PeerId, ReportSource};
 use slog::{crit, debug, error, info, trace, warn};
@@ -746,6 +747,16 @@ impl<T: BeaconChainTypes> Worker<T> {
                 self.propagate_validation_result(message_id, peer_id, MessageAcceptance::Ignore);
                 return None;
             }
+            // TODO: check that this is what we're supposed to do when we don't want to
+            //       penalize a peer for our configuration issue
+            // in the verification process BUT is this the proper way to handle it?
+            Err(e @BlockError::ExecutionPayloadError(ExecutionPayloadError::Eth1VerificationError(_)))
+            | Err(e @BlockError::ExecutionPayloadError(ExecutionPayloadError::NoEth1Connection)) => {
+                debug!(self.log, "Could not verify block for gossip, ignoring the block";
+                            "error" => %e);
+                self.propagate_validation_result(message_id, peer_id, MessageAcceptance::Ignore);
+                return;
+            }
             Err(e @ BlockError::StateRootMismatch { .. })
             | Err(e @ BlockError::IncorrectBlockProposer { .. })
             | Err(e @ BlockError::BlockSlotLimitReached)
@@ -759,6 +770,8 @@ impl<T: BeaconChainTypes> Worker<T> {
             | Err(e @ BlockError::TooManySkippedSlots { .. })
             | Err(e @ BlockError::WeakSubjectivityConflict)
             | Err(e @ BlockError::InconsistentFork(_))
+            // TODO: is this what we should be doing when block verification fails?
+            | Err(e @BlockError::ExecutionPayloadError(_))
             | Err(e @ BlockError::GenesisBlock) => {
                 warn!(self.log, "Could not verify block for gossip, rejecting the block";
                             "error" => %e);
diff --git a/beacon_node/store/src/hot_cold_store.rs b/beacon_node/store/src/hot_cold_store.rs
index 0194544c8..cfa49847d 100644
--- a/beacon_node/store/src/hot_cold_store.rs
+++ b/beacon_node/store/src/hot_cold_store.rs
@@ -883,6 +883,10 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
                         &mut block.message.state_root,
                         &mut block.message.parent_root,
                     ),
+                    SignedBeaconBlock::Merge(block) => (
+                        &mut block.message.state_root,
+                        &mut block.message.parent_root,
+                    ),
                 };
 
                 *state_root = Hash256::zero();
diff --git a/beacon_node/store/src/partial_beacon_state.rs b/beacon_node/store/src/partial_beacon_state.rs
index 9c8fcc4b7..010796afd 100644
--- a/beacon_node/store/src/partial_beacon_state.rs
+++ b/beacon_node/store/src/partial_beacon_state.rs
@@ -14,8 +14,8 @@ use types::*;
 ///
 /// Utilises lazy-loading from separate storage for its vector fields.
 #[superstruct(
-    variants(Base, Altair),
-    variant_attributes(derive(Debug, PartialEq, Clone, Encode, Decode),)
+    variants(Base, Altair, Merge),
+    variant_attributes(derive(Debug, PartialEq, Clone, Encode, Decode))
 )]
 #[derive(Debug, PartialEq, Clone, Encode)]
 #[ssz(enum_behaviour = "transparent")]
@@ -66,9 +66,9 @@ where
     pub current_epoch_attestations: VariableList<PendingAttestation<T>, T::MaxPendingAttestations>,
 
     // Participation (Altair and later)
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub previous_epoch_participation: VariableList<ParticipationFlags, T::ValidatorRegistryLimit>,
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub current_epoch_participation: VariableList<ParticipationFlags, T::ValidatorRegistryLimit>,
 
     // Finality
@@ -78,14 +78,18 @@ where
     pub finalized_checkpoint: Checkpoint,
 
     // Inactivity
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub inactivity_scores: VariableList<u64, T::ValidatorRegistryLimit>,
 
     // Light-client sync committees
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub current_sync_committee: Arc<SyncCommittee<T>>,
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub next_sync_committee: Arc<SyncCommittee<T>>,
+
+    // Execution
+    #[superstruct(only(Merge))]
+    pub latest_execution_payload_header: ExecutionPayloadHeader<T>,
 }
 
 /// Implement the conversion function from BeaconState -> PartialBeaconState.
@@ -160,6 +164,20 @@ impl<T: EthSpec> PartialBeaconState<T> {
                     inactivity_scores
                 ]
             ),
+            BeaconState::Merge(s) => impl_from_state_forgetful!(
+                s,
+                outer,
+                Merge,
+                PartialBeaconStateMerge,
+                [
+                    previous_epoch_participation,
+                    current_epoch_participation,
+                    current_sync_committee,
+                    next_sync_committee,
+                    inactivity_scores,
+                    latest_execution_payload_header
+                ]
+            ),
         }
     }
 
@@ -334,6 +352,19 @@ impl<E: EthSpec> TryInto<BeaconState<E>> for PartialBeaconState<E> {
                     inactivity_scores
                 ]
             ),
+            PartialBeaconState::Merge(inner) => impl_try_into_beacon_state!(
+                inner,
+                Merge,
+                BeaconStateMerge,
+                [
+                    previous_epoch_participation,
+                    current_epoch_participation,
+                    current_sync_committee,
+                    next_sync_committee,
+                    inactivity_scores,
+                    latest_execution_payload_header
+                ]
+            ),
         };
         Ok(state)
     }
diff --git a/consensus/fork_choice/Cargo.toml b/consensus/fork_choice/Cargo.toml
index f708045df..2bfe3f137 100644
--- a/consensus/fork_choice/Cargo.toml
+++ b/consensus/fork_choice/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2018"
 
 [dependencies]
 types = { path = "../types" }
+state_processing = { path = "../state_processing" }
 proto_array = { path = "../proto_array" }
 eth2_ssz = "0.4.0"
 eth2_ssz_derive = "0.3.0"
diff --git a/consensus/fork_choice/src/fork_choice.rs b/consensus/fork_choice/src/fork_choice.rs
index d0aa8abc1..f1b9a6999 100644
--- a/consensus/fork_choice/src/fork_choice.rs
+++ b/consensus/fork_choice/src/fork_choice.rs
@@ -2,9 +2,11 @@ use std::marker::PhantomData;
 
 use proto_array::{Block as ProtoBlock, ProtoArrayForkChoice};
 use ssz_derive::{Decode, Encode};
+use state_processing::per_block_processing::is_merge_block;
 use types::{
     AttestationShufflingId, BeaconBlock, BeaconState, BeaconStateError, ChainSpec, Checkpoint,
-    Epoch, EthSpec, Hash256, IndexedAttestation, RelativeEpoch, SignedBeaconBlock, Slot,
+    Epoch, EthSpec, Hash256, IndexedAttestation, PowBlock, RelativeEpoch, SignedBeaconBlock, Slot,
+    Uint256,
 };
 
 use crate::ForkChoiceStore;
@@ -60,6 +62,10 @@ pub enum InvalidBlock {
         finalized_root: Hash256,
         block_ancestor: Option<Hash256>,
     },
+    InvalidTerminalPowBlock {
+        block_total_difficulty: Uint256,
+        parent_total_difficulty: Uint256,
+    },
 }
 
 #[derive(Debug)]
@@ -231,6 +237,14 @@ where
     }
 }
 
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/fork-choice.md#is_valid_terminal_pow_block
+fn is_valid_terminal_pow_block(block: &PowBlock, parent: &PowBlock, spec: &ChainSpec) -> bool {
+    let is_total_difficulty_reached = block.total_difficulty >= spec.terminal_total_difficulty;
+    let is_parent_total_difficulty_valid = parent.total_difficulty < spec.terminal_total_difficulty;
+
+    is_total_difficulty_reached && is_parent_total_difficulty_valid
+}
+
 impl<T, E> ForkChoice<T, E>
 where
     T: ForkChoiceStore<E>,
@@ -489,6 +503,19 @@ where
             }));
         }
 
+        // https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/fork-choice.md#on_block
+        if is_merge_block(state, block.body()) {
+            // TODO: get POW blocks from eth1 chain here as indicated in the merge spec link ^
+            let pow_block = PowBlock::default();
+            let pow_parent = PowBlock::default();
+            if !is_valid_terminal_pow_block(&pow_block, &pow_parent, spec) {
+                return Err(Error::InvalidBlock(InvalidBlock::InvalidTerminalPowBlock {
+                    block_total_difficulty: pow_block.total_difficulty,
+                    parent_total_difficulty: pow_parent.total_difficulty,
+                }));
+            }
+        }
+
         // Update justified checkpoint.
         if state.current_justified_checkpoint().epoch > self.fc_store.justified_checkpoint().epoch {
             if state.current_justified_checkpoint().epoch
diff --git a/consensus/ssz/src/decode/impls.rs b/consensus/ssz/src/decode/impls.rs
index 29b2aec8e..0e6b39083 100644
--- a/consensus/ssz/src/decode/impls.rs
+++ b/consensus/ssz/src/decode/impls.rs
@@ -1,6 +1,6 @@
 use super::*;
 use core::num::NonZeroUsize;
-use ethereum_types::{H256, U128, U256};
+use ethereum_types::{H160, H256, U128, U256};
 use smallvec::SmallVec;
 use std::sync::Arc;
 
@@ -256,6 +256,27 @@ impl<T: Decode> Decode for Arc<T> {
     }
 }
 
+impl Decode for H160 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        20
+    }
+
+    fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        let len = bytes.len();
+        let expected = <Self as Decode>::ssz_fixed_len();
+
+        if len != expected {
+            Err(DecodeError::InvalidByteLength { len, expected })
+        } else {
+            Ok(Self::from_slice(bytes))
+        }
+    }
+}
+
 impl Decode for H256 {
     fn is_ssz_fixed_len() -> bool {
         true
diff --git a/consensus/ssz/src/encode/impls.rs b/consensus/ssz/src/encode/impls.rs
index 00d3e0a3a..5728685d0 100644
--- a/consensus/ssz/src/encode/impls.rs
+++ b/consensus/ssz/src/encode/impls.rs
@@ -1,6 +1,6 @@
 use super::*;
 use core::num::NonZeroUsize;
-use ethereum_types::{H256, U128, U256};
+use ethereum_types::{H160, H256, U128, U256};
 use smallvec::SmallVec;
 use std::sync::Arc;
 
@@ -305,6 +305,24 @@ impl Encode for NonZeroUsize {
     }
 }
 
+impl Encode for H160 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        20
+    }
+
+    fn ssz_bytes_len(&self) -> usize {
+        20
+    }
+
+    fn ssz_append(&self, buf: &mut Vec<u8>) {
+        buf.extend_from_slice(self.as_bytes());
+    }
+}
+
 impl Encode for H256 {
     fn is_ssz_fixed_len() -> bool {
         true
diff --git a/consensus/state_processing/src/common/slash_validator.rs b/consensus/state_processing/src/common/slash_validator.rs
index 7643043ba..237905a30 100644
--- a/consensus/state_processing/src/common/slash_validator.rs
+++ b/consensus/state_processing/src/common/slash_validator.rs
@@ -33,7 +33,7 @@ pub fn slash_validator<T: EthSpec>(
 
     let min_slashing_penalty_quotient = match state {
         BeaconState::Base(_) => spec.min_slashing_penalty_quotient,
-        BeaconState::Altair(_) => spec.min_slashing_penalty_quotient_altair,
+        BeaconState::Altair(_) | BeaconState::Merge(_) => spec.min_slashing_penalty_quotient_altair,
     };
     decrease_balance(
         state,
@@ -48,7 +48,7 @@ pub fn slash_validator<T: EthSpec>(
         validator_effective_balance.safe_div(spec.whistleblower_reward_quotient)?;
     let proposer_reward = match state {
         BeaconState::Base(_) => whistleblower_reward.safe_div(spec.proposer_reward_quotient)?,
-        BeaconState::Altair(_) => whistleblower_reward
+        BeaconState::Altair(_) | BeaconState::Merge(_) => whistleblower_reward
             .safe_mul(PROPOSER_WEIGHT)?
             .safe_div(WEIGHT_DENOMINATOR)?,
     };
diff --git a/consensus/state_processing/src/genesis.rs b/consensus/state_processing/src/genesis.rs
index 7834c6daf..b9f3c781a 100644
--- a/consensus/state_processing/src/genesis.rs
+++ b/consensus/state_processing/src/genesis.rs
@@ -52,6 +52,8 @@ pub fn initialize_beacon_state_from_eth1<T: EthSpec>(
         state.fork_mut().previous_version = spec.altair_fork_version;
     }
 
+    // TODO: handle upgrade_to_merge() here
+
     // Now that we have our validators, initialize the caches (including the committees)
     state.build_all_caches(spec)?;
 
diff --git a/consensus/state_processing/src/per_block_processing.rs b/consensus/state_processing/src/per_block_processing.rs
index 845aee747..29e5a7c46 100644
--- a/consensus/state_processing/src/per_block_processing.rs
+++ b/consensus/state_processing/src/per_block_processing.rs
@@ -149,6 +149,10 @@ pub fn per_block_processing<T: EthSpec>(
         )?;
     }
 
+    if is_execution_enabled(state, block.body()) {
+        process_execution_payload(state, block.body().execution_payload().unwrap(), spec)?
+    }
+
     Ok(())
 }
 
@@ -283,3 +287,135 @@ pub fn get_new_eth1_data<T: EthSpec>(
         Ok(None)
     }
 }
+
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#is_valid_gas_limit
+pub fn is_valid_gas_limit<T: EthSpec>(
+    payload: &ExecutionPayload<T>,
+    parent: &ExecutionPayloadHeader<T>,
+) -> bool {
+    // check if payload used too much gas
+    if payload.gas_used > payload.gas_limit {
+        return false;
+    }
+    // check if payload changed the gas limit too much
+    if payload.gas_limit >= parent.gas_limit + parent.gas_limit / T::gas_limit_denominator() {
+        return false;
+    }
+    if payload.gas_limit <= parent.gas_limit - parent.gas_limit / T::gas_limit_denominator() {
+        return false;
+    }
+    // check if the gas limit is at least the minimum gas limit
+    if payload.gas_limit < T::min_gas_limit() {
+        return false;
+    }
+
+    return true;
+}
+
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#process_execution_payload
+pub fn process_execution_payload<T: EthSpec>(
+    state: &mut BeaconState<T>,
+    payload: &ExecutionPayload<T>,
+    spec: &ChainSpec,
+) -> Result<(), BlockProcessingError> {
+    if is_merge_complete(state) {
+        block_verify!(
+            payload.parent_hash == state.latest_execution_payload_header()?.block_hash,
+            BlockProcessingError::ExecutionHashChainIncontiguous {
+                expected: state.latest_execution_payload_header()?.block_hash,
+                found: payload.parent_hash,
+            }
+        );
+        block_verify!(
+            payload.block_number
+                == state
+                    .latest_execution_payload_header()?
+                    .block_number
+                    .safe_add(1)?,
+            BlockProcessingError::ExecutionBlockNumberIncontiguous {
+                expected: state
+                    .latest_execution_payload_header()?
+                    .block_number
+                    .safe_add(1)?,
+                found: payload.block_number,
+            }
+        );
+        block_verify!(
+            payload.random == *state.get_randao_mix(state.current_epoch())?,
+            BlockProcessingError::ExecutionRandaoMismatch {
+                expected: *state.get_randao_mix(state.current_epoch())?,
+                found: payload.random,
+            }
+        );
+        block_verify!(
+            is_valid_gas_limit(payload, state.latest_execution_payload_header()?),
+            BlockProcessingError::ExecutionInvalidGasLimit {
+                used: payload.gas_used,
+                limit: payload.gas_limit,
+            }
+        );
+    }
+
+    let timestamp = compute_timestamp_at_slot(state, spec)?;
+    block_verify!(
+        payload.timestamp == timestamp,
+        BlockProcessingError::ExecutionInvalidTimestamp {
+            expected: timestamp,
+            found: payload.timestamp,
+        }
+    );
+
+    *state.latest_execution_payload_header_mut()? = ExecutionPayloadHeader {
+        parent_hash: payload.parent_hash,
+        coinbase: payload.coinbase,
+        state_root: payload.state_root,
+        receipt_root: payload.receipt_root,
+        logs_bloom: payload.logs_bloom.clone(),
+        random: payload.random,
+        block_number: payload.block_number,
+        gas_limit: payload.gas_limit,
+        gas_used: payload.gas_used,
+        timestamp: payload.timestamp,
+        base_fee_per_gas: payload.base_fee_per_gas,
+        block_hash: payload.block_hash,
+        transactions_root: payload.transactions.tree_hash_root(),
+    };
+
+    Ok(())
+}
+
+/// These functions will definitely be called before the merge. Their entire purpose is to check if
+/// the merge has happened or if we're on the transition block. Thus we don't want to propagate
+/// errors from the `BeaconState` being an earlier variant than `BeaconStateMerge` as we'd have to
+/// repeaetedly write code to treat these errors as false.
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#is_merge_complete
+pub fn is_merge_complete<T: EthSpec>(state: &BeaconState<T>) -> bool {
+    state
+        .latest_execution_payload_header()
+        .map(|header| *header != <ExecutionPayloadHeader<T>>::default())
+        .unwrap_or(false)
+}
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#is_merge_block
+pub fn is_merge_block<T: EthSpec>(state: &BeaconState<T>, body: BeaconBlockBodyRef<T>) -> bool {
+    body.execution_payload()
+        .map(|payload| !is_merge_complete(state) && *payload != <ExecutionPayload<T>>::default())
+        .unwrap_or(false)
+}
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#is_execution_enabled
+pub fn is_execution_enabled<T: EthSpec>(
+    state: &BeaconState<T>,
+    body: BeaconBlockBodyRef<T>,
+) -> bool {
+    is_merge_block(state, body) || is_merge_complete(state)
+}
+
+/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#compute_timestamp_at_slot
+pub fn compute_timestamp_at_slot<T: EthSpec>(
+    state: &BeaconState<T>,
+    spec: &ChainSpec,
+) -> Result<u64, ArithError> {
+    let slots_since_genesis = state.slot().as_u64().safe_sub(spec.genesis_slot.as_u64())?;
+    slots_since_genesis
+        .safe_mul(spec.seconds_per_slot)
+        .and_then(|since_genesis| state.genesis_time().safe_add(since_genesis))
+}
diff --git a/consensus/state_processing/src/per_block_processing/errors.rs b/consensus/state_processing/src/per_block_processing/errors.rs
index 2ba9ea78c..b6fa363e0 100644
--- a/consensus/state_processing/src/per_block_processing/errors.rs
+++ b/consensus/state_processing/src/per_block_processing/errors.rs
@@ -57,6 +57,26 @@ pub enum BlockProcessingError {
     ArithError(ArithError),
     InconsistentBlockFork(InconsistentFork),
     InconsistentStateFork(InconsistentFork),
+    ExecutionHashChainIncontiguous {
+        expected: Hash256,
+        found: Hash256,
+    },
+    ExecutionBlockNumberIncontiguous {
+        expected: u64,
+        found: u64,
+    },
+    ExecutionRandaoMismatch {
+        expected: Hash256,
+        found: Hash256,
+    },
+    ExecutionInvalidGasLimit {
+        used: u64,
+        limit: u64,
+    },
+    ExecutionInvalidTimestamp {
+        expected: u64,
+        found: u64,
+    },
 }
 
 impl From<BeaconStateError> for BlockProcessingError {
diff --git a/consensus/state_processing/src/per_block_processing/process_operations.rs b/consensus/state_processing/src/per_block_processing/process_operations.rs
index f2cef47d6..a4a0738eb 100644
--- a/consensus/state_processing/src/per_block_processing/process_operations.rs
+++ b/consensus/state_processing/src/per_block_processing/process_operations.rs
@@ -228,7 +228,7 @@ pub fn process_attestations<'a, T: EthSpec>(
         BeaconBlockBodyRef::Base(_) => {
             base::process_attestations(state, block_body.attestations(), verify_signatures, spec)?;
         }
-        BeaconBlockBodyRef::Altair(_) => {
+        BeaconBlockBodyRef::Altair(_) | BeaconBlockBodyRef::Merge(_) => {
             altair::process_attestations(
                 state,
                 block_body.attestations(),
diff --git a/consensus/state_processing/src/per_epoch_processing.rs b/consensus/state_processing/src/per_epoch_processing.rs
index 245876b86..d813dc42f 100644
--- a/consensus/state_processing/src/per_epoch_processing.rs
+++ b/consensus/state_processing/src/per_epoch_processing.rs
@@ -35,7 +35,7 @@ pub fn process_epoch<T: EthSpec>(
 
     match state {
         BeaconState::Base(_) => base::process_epoch(state, spec),
-        BeaconState::Altair(_) => altair::process_epoch(state, spec),
+        BeaconState::Altair(_) | BeaconState::Merge(_) => altair::process_epoch(state, spec),
     }
 }
 
diff --git a/consensus/state_processing/src/per_slot_processing.rs b/consensus/state_processing/src/per_slot_processing.rs
index 43eaa89c1..454cee5ff 100644
--- a/consensus/state_processing/src/per_slot_processing.rs
+++ b/consensus/state_processing/src/per_slot_processing.rs
@@ -1,4 +1,4 @@
-use crate::upgrade::upgrade_to_altair;
+use crate::upgrade::{upgrade_to_altair, upgrade_to_merge};
 use crate::{per_epoch_processing::EpochProcessingSummary, *};
 use safe_arith::{ArithError, SafeArith};
 use types::*;
@@ -44,11 +44,17 @@ pub fn per_slot_processing<T: EthSpec>(
 
     state.slot_mut().safe_add_assign(1)?;
 
-    // If the Altair fork epoch is reached, perform an irregular state upgrade.
-    if state.slot().safe_rem(T::slots_per_epoch())? == 0
-        && spec.altair_fork_epoch == Some(state.current_epoch())
-    {
-        upgrade_to_altair(state, spec)?;
+    // Process fork upgrades here. Note that multiple upgrades can potentially run
+    // in sequence if they are scheduled in the same Epoch (common in testnets)
+    if state.slot().safe_rem(T::slots_per_epoch())? == 0 {
+        // If the Altair fork epoch is reached, perform an irregular state upgrade.
+        if spec.altair_fork_epoch == Some(state.current_epoch()) {
+            upgrade_to_altair(state, spec)?;
+        }
+        // If the Merge fork epoch is reached, perform an irregular state upgrade.
+        if spec.merge_fork_epoch == Some(state.current_epoch()) {
+            upgrade_to_merge(state, spec)?;
+        }
     }
 
     Ok(summary)
diff --git a/consensus/state_processing/src/upgrade.rs b/consensus/state_processing/src/upgrade.rs
index ca8e51596..fda1a714a 100644
--- a/consensus/state_processing/src/upgrade.rs
+++ b/consensus/state_processing/src/upgrade.rs
@@ -1,3 +1,5 @@
 pub mod altair;
+pub mod merge;
 
 pub use altair::upgrade_to_altair;
+pub use merge::upgrade_to_merge;
diff --git a/consensus/state_processing/src/upgrade/merge.rs b/consensus/state_processing/src/upgrade/merge.rs
new file mode 100644
index 000000000..c41987609
--- /dev/null
+++ b/consensus/state_processing/src/upgrade/merge.rs
@@ -0,0 +1,72 @@
+use std::mem;
+use types::{
+    BeaconState, BeaconStateError as Error, BeaconStateMerge, ChainSpec, EthSpec,
+    ExecutionPayloadHeader, Fork,
+};
+
+/// Transform a `Altair` state into an `Merge` state.
+pub fn upgrade_to_merge<E: EthSpec>(
+    pre_state: &mut BeaconState<E>,
+    spec: &ChainSpec,
+) -> Result<(), Error> {
+    let epoch = pre_state.current_epoch();
+    let pre = pre_state.as_altair_mut()?;
+
+    // Where possible, use something like `mem::take` to move fields from behind the &mut
+    // reference. For other fields that don't have a good default value, use `clone`.
+    //
+    // Fixed size vectors get cloned because replacing them would require the same size
+    // allocation as cloning.
+    let post = BeaconState::Merge(BeaconStateMerge {
+        // Versioning
+        genesis_time: pre.genesis_time,
+        genesis_validators_root: pre.genesis_validators_root,
+        slot: pre.slot,
+        fork: Fork {
+            previous_version: pre.fork.current_version,
+            current_version: spec.merge_fork_version,
+            epoch,
+        },
+        // History
+        latest_block_header: pre.latest_block_header.clone(),
+        block_roots: pre.block_roots.clone(),
+        state_roots: pre.state_roots.clone(),
+        historical_roots: mem::take(&mut pre.historical_roots),
+        // Eth1
+        eth1_data: pre.eth1_data.clone(),
+        eth1_data_votes: mem::take(&mut pre.eth1_data_votes),
+        eth1_deposit_index: pre.eth1_deposit_index,
+        // Registry
+        validators: mem::take(&mut pre.validators),
+        balances: mem::take(&mut pre.balances),
+        // Randomness
+        randao_mixes: pre.randao_mixes.clone(),
+        // Slashings
+        slashings: pre.slashings.clone(),
+        // `Participation
+        previous_epoch_participation: mem::take(&mut pre.previous_epoch_participation),
+        current_epoch_participation: mem::take(&mut pre.current_epoch_participation),
+        // Finality
+        justification_bits: pre.justification_bits.clone(),
+        previous_justified_checkpoint: pre.previous_justified_checkpoint,
+        current_justified_checkpoint: pre.current_justified_checkpoint,
+        finalized_checkpoint: pre.finalized_checkpoint,
+        // Inactivity
+        inactivity_scores: mem::take(&mut pre.inactivity_scores),
+        // Sync committees
+        current_sync_committee: pre.current_sync_committee.clone(),
+        next_sync_committee: pre.next_sync_committee.clone(),
+        // Execution
+        latest_execution_payload_header: <ExecutionPayloadHeader<E>>::default(),
+        // Caches
+        total_active_balance: pre.total_active_balance,
+        committee_caches: mem::take(&mut pre.committee_caches),
+        pubkey_cache: mem::take(&mut pre.pubkey_cache),
+        exit_cache: mem::take(&mut pre.exit_cache),
+        tree_hash_cache: mem::take(&mut pre.tree_hash_cache),
+    });
+
+    *pre_state = post;
+
+    Ok(())
+}
diff --git a/consensus/tree_hash/src/impls.rs b/consensus/tree_hash/src/impls.rs
index 7fdcfceb7..00fed489c 100644
--- a/consensus/tree_hash/src/impls.rs
+++ b/consensus/tree_hash/src/impls.rs
@@ -1,5 +1,5 @@
 use super::*;
-use ethereum_types::{H256, U128, U256};
+use ethereum_types::{H160, H256, U128, U256};
 
 fn int_to_hash256(int: u64) -> Hash256 {
     let mut bytes = [0; HASHSIZE];
@@ -126,6 +126,28 @@ impl TreeHash for U256 {
     }
 }
 
+impl TreeHash for H160 {
+    fn tree_hash_type() -> TreeHashType {
+        TreeHashType::Vector
+    }
+
+    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+        let mut result = vec![0; 32];
+        result[0..20].copy_from_slice(self.as_bytes());
+        result
+    }
+
+    fn tree_hash_packing_factor() -> usize {
+        1
+    }
+
+    fn tree_hash_root(&self) -> Hash256 {
+        let mut result = [0; 32];
+        result[0..20].copy_from_slice(self.as_bytes());
+        Hash256::from_slice(&result)
+    }
+}
+
 impl TreeHash for H256 {
     fn tree_hash_type() -> TreeHashType {
         TreeHashType::Vector
diff --git a/consensus/types/src/beacon_block.rs b/consensus/types/src/beacon_block.rs
index f11b92148..cc706224c 100644
--- a/consensus/types/src/beacon_block.rs
+++ b/consensus/types/src/beacon_block.rs
@@ -1,5 +1,6 @@
 use crate::beacon_block_body::{
-    BeaconBlockBodyAltair, BeaconBlockBodyBase, BeaconBlockBodyRef, BeaconBlockBodyRefMut,
+    BeaconBlockBodyAltair, BeaconBlockBodyBase, BeaconBlockBodyMerge, BeaconBlockBodyRef,
+    BeaconBlockBodyRefMut,
 };
 use crate::test_utils::TestRandom;
 use crate::*;
@@ -14,7 +15,7 @@ use tree_hash_derive::TreeHash;
 
 /// A block of the `BeaconChain`.
 #[superstruct(
-    variants(Base, Altair),
+    variants(Base, Altair, Merge),
     variant_attributes(
         derive(
             Debug,
@@ -55,6 +56,8 @@ pub struct BeaconBlock<T: EthSpec> {
     pub body: BeaconBlockBodyBase<T>,
     #[superstruct(only(Altair), partial_getter(rename = "body_altair"))]
     pub body: BeaconBlockBodyAltair<T>,
+    #[superstruct(only(Merge), partial_getter(rename = "body_merge"))]
+    pub body: BeaconBlockBodyMerge<T>,
 }
 
 impl<T: EthSpec> SignedRoot for BeaconBlock<T> {}
@@ -63,7 +66,9 @@ impl<'a, T: EthSpec> SignedRoot for BeaconBlockRef<'a, T> {}
 impl<T: EthSpec> BeaconBlock<T> {
     /// Returns an empty block to be used during genesis.
     pub fn empty(spec: &ChainSpec) -> Self {
-        if spec.altair_fork_epoch == Some(T::genesis_epoch()) {
+        if spec.merge_fork_epoch == Some(T::genesis_epoch()) {
+            Self::Merge(BeaconBlockMerge::empty(spec))
+        } else if spec.altair_fork_epoch == Some(T::genesis_epoch()) {
             Self::Altair(BeaconBlockAltair::empty(spec))
         } else {
             Self::Base(BeaconBlockBase::empty(spec))
@@ -171,6 +176,7 @@ impl<'a, T: EthSpec> BeaconBlockRef<'a, T> {
         let object_fork = match self {
             BeaconBlockRef::Base { .. } => ForkName::Base,
             BeaconBlockRef::Altair { .. } => ForkName::Altair,
+            BeaconBlockRef::Merge { .. } => ForkName::Merge,
         };
 
         if fork_at_slot == object_fork {
@@ -188,6 +194,7 @@ impl<'a, T: EthSpec> BeaconBlockRef<'a, T> {
         match self {
             BeaconBlockRef::Base(block) => BeaconBlockBodyRef::Base(&block.body),
             BeaconBlockRef::Altair(block) => BeaconBlockBodyRef::Altair(&block.body),
+            BeaconBlockRef::Merge(block) => BeaconBlockBodyRef::Merge(&block.body),
         }
     }
 
@@ -196,6 +203,7 @@ impl<'a, T: EthSpec> BeaconBlockRef<'a, T> {
         match self {
             BeaconBlockRef::Base(block) => block.body.tree_hash_root(),
             BeaconBlockRef::Altair(block) => block.body.tree_hash_root(),
+            BeaconBlockRef::Merge(block) => block.body.tree_hash_root(),
         }
     }
 
@@ -230,6 +238,7 @@ impl<'a, T: EthSpec> BeaconBlockRefMut<'a, T> {
         match self {
             BeaconBlockRefMut::Base(block) => BeaconBlockBodyRefMut::Base(&mut block.body),
             BeaconBlockRefMut::Altair(block) => BeaconBlockBodyRefMut::Altair(&mut block.body),
+            BeaconBlockRefMut::Merge(block) => BeaconBlockBodyRefMut::Merge(&mut block.body),
         }
     }
 }
@@ -411,6 +420,61 @@ impl<T: EthSpec> BeaconBlockAltair<T> {
     }
 }
 
+impl<T: EthSpec> BeaconBlockMerge<T> {
+    /// Returns an empty Merge block to be used during genesis.
+    pub fn empty(spec: &ChainSpec) -> Self {
+        BeaconBlockMerge {
+            slot: spec.genesis_slot,
+            proposer_index: 0,
+            parent_root: Hash256::zero(),
+            state_root: Hash256::zero(),
+            body: BeaconBlockBodyMerge {
+                randao_reveal: Signature::empty(),
+                eth1_data: Eth1Data {
+                    deposit_root: Hash256::zero(),
+                    block_hash: Hash256::zero(),
+                    deposit_count: 0,
+                },
+                graffiti: Graffiti::default(),
+                proposer_slashings: VariableList::empty(),
+                attester_slashings: VariableList::empty(),
+                attestations: VariableList::empty(),
+                deposits: VariableList::empty(),
+                voluntary_exits: VariableList::empty(),
+                sync_aggregate: SyncAggregate::empty(),
+                execution_payload: ExecutionPayload::empty(),
+            },
+        }
+    }
+
+    /// Return an Merge block where the block has maximum size.
+    pub fn full(spec: &ChainSpec) -> Self {
+        let altair_block = BeaconBlockAltair::full(spec);
+        BeaconBlockMerge {
+            slot: spec.genesis_slot,
+            proposer_index: 0,
+            parent_root: Hash256::zero(),
+            state_root: Hash256::zero(),
+            body: BeaconBlockBodyMerge {
+                proposer_slashings: altair_block.body.proposer_slashings,
+                attester_slashings: altair_block.body.attester_slashings,
+                attestations: altair_block.body.attestations,
+                deposits: altair_block.body.deposits,
+                voluntary_exits: altair_block.body.voluntary_exits,
+                sync_aggregate: altair_block.body.sync_aggregate,
+                randao_reveal: Signature::empty(),
+                eth1_data: Eth1Data {
+                    deposit_root: Hash256::zero(),
+                    block_hash: Hash256::zero(),
+                    deposit_count: 0,
+                },
+                graffiti: Graffiti::default(),
+                execution_payload: ExecutionPayload::default(),
+            },
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/consensus/types/src/beacon_block_body.rs b/consensus/types/src/beacon_block_body.rs
index ceb90fef9..3b417f5d0 100644
--- a/consensus/types/src/beacon_block_body.rs
+++ b/consensus/types/src/beacon_block_body.rs
@@ -11,7 +11,7 @@ use tree_hash_derive::TreeHash;
 ///
 /// This *superstruct* abstracts over the hard-fork.
 #[superstruct(
-    variants(Base, Altair),
+    variants(Base, Altair, Merge),
     variant_attributes(
         derive(
             Debug,
@@ -26,7 +26,9 @@ use tree_hash_derive::TreeHash;
         ),
         serde(bound = "T: EthSpec", deny_unknown_fields),
         cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))
-    )
+    ),
+    cast_error(ty = "Error", expr = "Error::IncorrectStateVariant"),
+    partial_getter_error(ty = "Error", expr = "Error::IncorrectStateVariant")
 )]
 #[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
 #[serde(untagged)]
@@ -41,8 +43,10 @@ pub struct BeaconBlockBody<T: EthSpec> {
     pub attestations: VariableList<Attestation<T>, T::MaxAttestations>,
     pub deposits: VariableList<Deposit, T::MaxDeposits>,
     pub voluntary_exits: VariableList<SignedVoluntaryExit, T::MaxVoluntaryExits>,
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub sync_aggregate: SyncAggregate<T>,
+    #[superstruct(only(Merge))]
+    pub execution_payload: ExecutionPayload<T>,
 }
 
 impl<'a, T: EthSpec> BeaconBlockBodyRef<'a, T> {
@@ -51,6 +55,25 @@ impl<'a, T: EthSpec> BeaconBlockBodyRef<'a, T> {
         match self {
             BeaconBlockBodyRef::Base(_) => None,
             BeaconBlockBodyRef::Altair(inner) => Some(&inner.sync_aggregate),
+            BeaconBlockBodyRef::Merge(inner) => Some(&inner.sync_aggregate),
+        }
+    }
+
+    /// Access the execution payload from the block's body, if one exists.
+    pub fn execution_payload(self) -> Option<&'a ExecutionPayload<T>> {
+        match self {
+            BeaconBlockBodyRef::Base(_) => None,
+            BeaconBlockBodyRef::Altair(_) => None,
+            BeaconBlockBodyRef::Merge(inner) => Some(&inner.execution_payload),
+        }
+    }
+
+    /// Get the fork_name of this object
+    pub fn fork_name(self) -> ForkName {
+        match self {
+            BeaconBlockBodyRef::Base { .. } => ForkName::Base,
+            BeaconBlockBodyRef::Altair { .. } => ForkName::Altair,
+            BeaconBlockBodyRef::Merge { .. } => ForkName::Merge,
         }
     }
 }
diff --git a/consensus/types/src/beacon_state.rs b/consensus/types/src/beacon_state.rs
index a12f35143..2c1c2a651 100644
--- a/consensus/types/src/beacon_state.rs
+++ b/consensus/types/src/beacon_state.rs
@@ -172,7 +172,7 @@ impl From<BeaconStateHash> for Hash256 {
 
 /// The state of the `BeaconChain` at some slot.
 #[superstruct(
-    variants(Base, Altair),
+    variants(Base, Altair, Merge),
     variant_attributes(
         derive(
             Derivative,
@@ -250,9 +250,9 @@ where
     pub current_epoch_attestations: VariableList<PendingAttestation<T>, T::MaxPendingAttestations>,
 
     // Participation (Altair and later)
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub previous_epoch_participation: VariableList<ParticipationFlags, T::ValidatorRegistryLimit>,
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub current_epoch_participation: VariableList<ParticipationFlags, T::ValidatorRegistryLimit>,
 
     // Finality
@@ -267,15 +267,19 @@ where
 
     // Inactivity
     #[serde(with = "ssz_types::serde_utils::quoted_u64_var_list")]
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub inactivity_scores: VariableList<u64, T::ValidatorRegistryLimit>,
 
     // Light-client sync committees
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub current_sync_committee: Arc<SyncCommittee<T>>,
-    #[superstruct(only(Altair))]
+    #[superstruct(only(Altair, Merge))]
     pub next_sync_committee: Arc<SyncCommittee<T>>,
 
+    // Execution
+    #[superstruct(only(Merge))]
+    pub latest_execution_payload_header: ExecutionPayloadHeader<T>,
+
     // Caching (not in the spec)
     #[serde(skip_serializing, skip_deserializing)]
     #[ssz(skip_serializing, skip_deserializing)]
@@ -384,6 +388,7 @@ impl<T: EthSpec> BeaconState<T> {
         let object_fork = match self {
             BeaconState::Base { .. } => ForkName::Base,
             BeaconState::Altair { .. } => ForkName::Altair,
+            BeaconState::Merge { .. } => ForkName::Merge,
         };
 
         if fork_at_slot == object_fork {
@@ -1089,6 +1094,7 @@ impl<T: EthSpec> BeaconState<T> {
         match self {
             BeaconState::Base(state) => (&mut state.validators, &mut state.balances),
             BeaconState::Altair(state) => (&mut state.validators, &mut state.balances),
+            BeaconState::Merge(state) => (&mut state.validators, &mut state.balances),
         }
     }
 
@@ -1284,11 +1290,13 @@ impl<T: EthSpec> BeaconState<T> {
             match self {
                 BeaconState::Base(_) => Err(BeaconStateError::IncorrectStateVariant),
                 BeaconState::Altair(state) => Ok(&mut state.current_epoch_participation),
+                BeaconState::Merge(state) => Ok(&mut state.current_epoch_participation),
             }
         } else if epoch == self.previous_epoch() {
             match self {
                 BeaconState::Base(_) => Err(BeaconStateError::IncorrectStateVariant),
                 BeaconState::Altair(state) => Ok(&mut state.previous_epoch_participation),
+                BeaconState::Merge(state) => Ok(&mut state.previous_epoch_participation),
             }
         } else {
             Err(BeaconStateError::EpochOutOfBounds)
@@ -1572,6 +1580,7 @@ impl<T: EthSpec> BeaconState<T> {
         let mut res = match self {
             BeaconState::Base(inner) => BeaconState::Base(inner.clone()),
             BeaconState::Altair(inner) => BeaconState::Altair(inner.clone()),
+            BeaconState::Merge(inner) => BeaconState::Merge(inner.clone()),
         };
         if config.committee_caches {
             *res.committee_caches_mut() = self.committee_caches().clone();
diff --git a/consensus/types/src/chain_spec.rs b/consensus/types/src/chain_spec.rs
index ee213f1f8..812c998be 100644
--- a/consensus/types/src/chain_spec.rs
+++ b/consensus/types/src/chain_spec.rs
@@ -127,6 +127,10 @@ pub struct ChainSpec {
     pub altair_fork_version: [u8; 4],
     /// The Altair fork epoch is optional, with `None` representing "Altair never happens".
     pub altair_fork_epoch: Option<Epoch>,
+    pub merge_fork_version: [u8; 4],
+    /// The Merge fork epoch is optional, with `None` representing "Merge never happens".
+    pub merge_fork_epoch: Option<Epoch>,
+    pub terminal_total_difficulty: Uint256,
 
     /*
      * Networking
@@ -156,7 +160,7 @@ impl ChainSpec {
     ) -> EnrForkId {
         EnrForkId {
             fork_digest: self.fork_digest::<T>(slot, genesis_validators_root),
-            next_fork_version: self.next_fork_version(),
+            next_fork_version: self.next_fork_version::<T>(slot),
             next_fork_epoch: self
                 .next_fork_epoch::<T>(slot)
                 .map(|(_, e)| e)
@@ -178,10 +182,12 @@ impl ChainSpec {
 
     /// Returns the `next_fork_version`.
     ///
-    /// Since `next_fork_version = current_fork_version` if no future fork is planned,
-    /// this function returns `altair_fork_version` until the next fork is planned.
-    pub fn next_fork_version(&self) -> [u8; 4] {
-        self.altair_fork_version
+    /// `next_fork_version = current_fork_version` if no future fork is planned,
+    pub fn next_fork_version<E: EthSpec>(&self, slot: Slot) -> [u8; 4] {
+        match self.next_fork_epoch::<E>(slot) {
+            Some((fork, _)) => self.fork_version_for_name(fork),
+            None => self.fork_version_for_name(self.fork_name_at_slot::<E>(slot)),
+        }
     }
 
     /// Returns the epoch of the next scheduled fork along with its corresponding `ForkName`.
@@ -201,9 +207,12 @@ impl ChainSpec {
 
     /// Returns the name of the fork which is active at `epoch`.
     pub fn fork_name_at_epoch(&self, epoch: Epoch) -> ForkName {
-        match self.altair_fork_epoch {
-            Some(fork_epoch) if epoch >= fork_epoch => ForkName::Altair,
-            _ => ForkName::Base,
+        match self.merge_fork_epoch {
+            Some(fork_epoch) if epoch >= fork_epoch => ForkName::Merge,
+            _ => match self.altair_fork_epoch {
+                Some(fork_epoch) if epoch >= fork_epoch => ForkName::Altair,
+                _ => ForkName::Base,
+            },
         }
     }
 
@@ -212,6 +221,7 @@ impl ChainSpec {
         match fork_name {
             ForkName::Base => self.genesis_fork_version,
             ForkName::Altair => self.altair_fork_version,
+            ForkName::Merge => self.merge_fork_version,
         }
     }
 
@@ -220,6 +230,7 @@ impl ChainSpec {
         match fork_name {
             ForkName::Base => Some(Epoch::new(0)),
             ForkName::Altair => self.altair_fork_epoch,
+            ForkName::Merge => self.merge_fork_epoch,
         }
     }
 
@@ -467,6 +478,9 @@ impl ChainSpec {
             domain_contribution_and_proof: 9,
             altair_fork_version: [0x01, 0x00, 0x00, 0x00],
             altair_fork_epoch: Some(Epoch::new(74240)),
+            merge_fork_version: [0x02, 0x00, 0x00, 0x00],
+            merge_fork_epoch: None,
+            terminal_total_difficulty: Uint256::MAX,
 
             /*
              * Network specific
diff --git a/consensus/types/src/consts.rs b/consensus/types/src/consts.rs
index 04e8e60ee..6088086ca 100644
--- a/consensus/types/src/consts.rs
+++ b/consensus/types/src/consts.rs
@@ -19,3 +19,13 @@ pub mod altair {
 
     pub const NUM_FLAG_INDICES: usize = 3;
 }
+
+pub mod merge_testing {
+    use ethereum_types::H256;
+    pub const GENESIS_GAS_LIMIT: u64 = 30_000_000;
+    pub const GENESIS_BASE_FEE_PER_GAS: H256 = H256([
+        0x00, 0xca, 0x9a, 0x3b, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00,
+    ]);
+}
diff --git a/consensus/types/src/eth_spec.rs b/consensus/types/src/eth_spec.rs
index 6e21edf9f..c45ecf8f7 100644
--- a/consensus/types/src/eth_spec.rs
+++ b/consensus/types/src/eth_spec.rs
@@ -9,6 +9,9 @@ use ssz_types::typenum::{
 use std::fmt::{self, Debug};
 use std::str::FromStr;
 
+use ssz_types::typenum::{bit::B0, UInt, U1048576, U16384, U256, U625};
+pub type U5000 = UInt<UInt<UInt<U625, B0>, B0>, B0>; // 625 * 8 = 5000
+
 const MAINNET: &str = "mainnet";
 const MINIMAL: &str = "minimal";
 
@@ -80,6 +83,14 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
     type SyncCommitteeSize: Unsigned + Clone + Sync + Send + Debug + PartialEq;
     /// The number of `sync_committee` subnets.
     type SyncCommitteeSubnetCount: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    /*
+     * New in Merge
+     */
+    type MaxBytesPerOpaqueTransaction: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    type MaxTransactionsPerPayload: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    type BytesPerLogsBloom: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    type GasLimitDenominator: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    type MinGasLimit: Unsigned + Clone + Sync + Send + Debug + PartialEq;
     /*
      * Derived values (set these CAREFULLY)
      */
@@ -187,6 +198,31 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
     fn sync_subcommittee_size() -> usize {
         Self::SyncSubcommitteeSize::to_usize()
     }
+
+    /// Returns the `MAX_BYTES_PER_OPAQUE_TRANSACTION` constant for this specification.
+    fn max_bytes_per_opaque_transaction() -> usize {
+        Self::MaxBytesPerOpaqueTransaction::to_usize()
+    }
+
+    /// Returns the `MAX_TRANSACTIONS_PER_PAYLOAD` constant for this specification.
+    fn max_transactions_per_payload() -> usize {
+        Self::MaxTransactionsPerPayload::to_usize()
+    }
+
+    /// Returns the `BYTES_PER_LOGS_BLOOM` constant for this specification.
+    fn bytes_per_logs_bloom() -> usize {
+        Self::BytesPerLogsBloom::to_usize()
+    }
+
+    /// Returns the `GAS_LIMIT_DENOMINATOR` constant for this specification.
+    fn gas_limit_denominator() -> u64 {
+        Self::GasLimitDenominator::to_u64()
+    }
+
+    /// Returns the `MIN_GAS_LIMIT` constant for this specification.
+    fn min_gas_limit() -> u64 {
+        Self::MinGasLimit::to_u64()
+    }
 }
 
 /// Macro to inherit some type values from another EthSpec.
@@ -221,6 +257,11 @@ impl EthSpec for MainnetEthSpec {
     type MaxVoluntaryExits = U16;
     type SyncCommitteeSize = U512;
     type SyncCommitteeSubnetCount = U4;
+    type MaxBytesPerOpaqueTransaction = U1048576;
+    type MaxTransactionsPerPayload = U16384;
+    type BytesPerLogsBloom = U256;
+    type GasLimitDenominator = U1024;
+    type MinGasLimit = U5000;
     type SyncSubcommitteeSize = U128; // 512 committee size / 4 sync committee subnet count
     type MaxPendingAttestations = U4096; // 128 max attestations * 32 slots per epoch
     type SlotsPerEth1VotingPeriod = U2048; // 64 epochs * 32 slots per epoch
@@ -262,7 +303,12 @@ impl EthSpec for MinimalEthSpec {
         MaxAttesterSlashings,
         MaxAttestations,
         MaxDeposits,
-        MaxVoluntaryExits
+        MaxVoluntaryExits,
+        MaxBytesPerOpaqueTransaction,
+        MaxTransactionsPerPayload,
+        BytesPerLogsBloom,
+        GasLimitDenominator,
+        MinGasLimit
     });
 
     fn default_spec() -> ChainSpec {
diff --git a/consensus/types/src/execution_payload.rs b/consensus/types/src/execution_payload.rs
new file mode 100644
index 000000000..bb0915098
--- /dev/null
+++ b/consensus/types/src/execution_payload.rs
@@ -0,0 +1,174 @@
+use crate::{test_utils::TestRandom, *};
+use serde_derive::{Deserialize, Serialize};
+use ssz_derive::{Decode, Encode};
+use std::{ops::Index, slice::SliceIndex};
+use test_random_derive::TestRandom;
+use tree_hash_derive::TreeHash;
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Encode, Decode, TreeHash)]
+#[ssz(enum_behaviour = "union")]
+#[tree_hash(enum_behaviour = "union")]
+pub enum Transaction<T: EthSpec> {
+    OpaqueTransaction(VariableList<u8, T::MaxBytesPerOpaqueTransaction>),
+}
+
+impl<T: EthSpec, I: SliceIndex<[u8]>> Index<I> for Transaction<T> {
+    type Output = I::Output;
+
+    #[inline]
+    fn index(&self, index: I) -> &Self::Output {
+        match self {
+            Self::OpaqueTransaction(v) => Index::index(v, index),
+        }
+    }
+}
+
+impl<T: EthSpec> From<VariableList<u8, T::MaxBytesPerOpaqueTransaction>> for Transaction<T> {
+    fn from(list: VariableList<u8, <T as EthSpec>::MaxBytesPerOpaqueTransaction>) -> Self {
+        Self::OpaqueTransaction(list)
+    }
+}
+
+#[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
+#[derive(
+    Default, Debug, Clone, PartialEq, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
+pub struct ExecutionPayload<T: EthSpec> {
+    pub parent_hash: Hash256,
+    pub coinbase: Address,
+    pub state_root: Hash256,
+    pub receipt_root: Hash256,
+    #[serde(with = "serde_logs_bloom")]
+    pub logs_bloom: FixedVector<u8, T::BytesPerLogsBloom>,
+    pub random: Hash256,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub block_number: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub gas_limit: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub gas_used: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub timestamp: u64,
+    pub base_fee_per_gas: Hash256,
+    pub block_hash: Hash256,
+    #[serde(with = "serde_transactions")]
+    #[test_random(default)]
+    pub transactions: VariableList<Transaction<T>, T::MaxTransactionsPerPayload>,
+}
+
+impl<T: EthSpec> ExecutionPayload<T> {
+    // TODO: check this whole thing later
+    pub fn empty() -> Self {
+        Self {
+            parent_hash: Hash256::zero(),
+            coinbase: Address::default(),
+            state_root: Hash256::zero(),
+            receipt_root: Hash256::zero(),
+            logs_bloom: FixedVector::default(),
+            random: Hash256::zero(),
+            block_number: 0,
+            gas_limit: 0,
+            gas_used: 0,
+            timestamp: 0,
+            base_fee_per_gas: Hash256::zero(),
+            block_hash: Hash256::zero(),
+            transactions: VariableList::empty(),
+        }
+    }
+}
+
+/// Serializes the `logs_bloom` field.
+pub mod serde_logs_bloom {
+    use super::*;
+    use eth2_serde_utils::hex::PrefixedHexVisitor;
+    use serde::{Deserializer, Serializer};
+
+    pub fn serialize<S, U>(bytes: &FixedVector<u8, U>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+        U: Unsigned,
+    {
+        let mut hex_string: String = "0x".to_string();
+        hex_string.push_str(&hex::encode(&bytes[..]));
+
+        serializer.serialize_str(&hex_string)
+    }
+
+    pub fn deserialize<'de, D, U>(deserializer: D) -> Result<FixedVector<u8, U>, D::Error>
+    where
+        D: Deserializer<'de>,
+        U: Unsigned,
+    {
+        let vec = deserializer.deserialize_string(PrefixedHexVisitor)?;
+
+        FixedVector::new(vec)
+            .map_err(|e| serde::de::Error::custom(format!("invalid logs bloom: {:?}", e)))
+    }
+}
+
+/// Serializes the `transactions` field.
+pub mod serde_transactions {
+    use super::*;
+    use eth2_serde_utils::hex;
+    use serde::ser::SerializeSeq;
+    use serde::{de, Deserializer, Serializer};
+    use std::marker::PhantomData;
+
+    pub struct ListOfBytesListVisitor<T: EthSpec> {
+        _t: PhantomData<T>,
+    }
+    impl<'a, T> serde::de::Visitor<'a> for ListOfBytesListVisitor<T>
+    where
+        T: EthSpec,
+    {
+        type Value = VariableList<Transaction<T>, T::MaxTransactionsPerPayload>;
+
+        fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+            write!(formatter, "a list of 0x-prefixed byte lists")
+        }
+
+        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+        where
+            A: serde::de::SeqAccess<'a>,
+        {
+            let mut outer = VariableList::default();
+
+            while let Some(val) = seq.next_element::<String>()? {
+                let inner_vec = hex::decode(&val).map_err(de::Error::custom)?;
+                let inner = VariableList::new(inner_vec).map_err(|e| {
+                    serde::de::Error::custom(format!("invalid transaction: {:?}", e))
+                })?;
+                outer.push(inner.into()).map_err(|e| {
+                    serde::de::Error::custom(format!("too many transactions: {:?}", e))
+                })?;
+            }
+
+            Ok(outer)
+        }
+    }
+
+    pub fn serialize<S, T>(
+        value: &VariableList<Transaction<T>, T::MaxTransactionsPerPayload>,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+        T: EthSpec,
+    {
+        let mut seq = serializer.serialize_seq(Some(value.len()))?;
+        for val in value {
+            seq.serialize_element(&hex::encode(&val[..]))?;
+        }
+        seq.end()
+    }
+
+    pub fn deserialize<'de, D, T>(
+        deserializer: D,
+    ) -> Result<VariableList<Transaction<T>, T::MaxTransactionsPerPayload>, D::Error>
+    where
+        D: Deserializer<'de>,
+        T: EthSpec,
+    {
+        deserializer.deserialize_any(ListOfBytesListVisitor { _t: PhantomData })
+    }
+}
diff --git a/consensus/types/src/execution_payload_header.rs b/consensus/types/src/execution_payload_header.rs
new file mode 100644
index 000000000..f0340eff6
--- /dev/null
+++ b/consensus/types/src/execution_payload_header.rs
@@ -0,0 +1,37 @@
+use crate::{execution_payload::serde_logs_bloom, test_utils::TestRandom, *};
+use serde_derive::{Deserialize, Serialize};
+use ssz_derive::{Decode, Encode};
+use test_random_derive::TestRandom;
+use tree_hash_derive::TreeHash;
+
+#[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
+#[derive(
+    Default, Debug, Clone, PartialEq, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
+pub struct ExecutionPayloadHeader<T: EthSpec> {
+    pub parent_hash: Hash256,
+    pub coinbase: Address,
+    pub state_root: Hash256,
+    pub receipt_root: Hash256,
+    #[serde(with = "serde_logs_bloom")]
+    pub logs_bloom: FixedVector<u8, T::BytesPerLogsBloom>,
+    pub random: Hash256,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub block_number: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub gas_limit: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub gas_used: u64,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub timestamp: u64,
+    pub base_fee_per_gas: Hash256,
+    pub block_hash: Hash256,
+    pub transactions_root: Hash256,
+}
+
+impl<T: EthSpec> ExecutionPayloadHeader<T> {
+    // TODO: check this whole thing later
+    pub fn empty() -> Self {
+        Self::default()
+    }
+}
diff --git a/consensus/types/src/fork_context.rs b/consensus/types/src/fork_context.rs
index 1d488f769..88a2f3126 100644
--- a/consensus/types/src/fork_context.rs
+++ b/consensus/types/src/fork_context.rs
@@ -35,6 +35,15 @@ impl ForkContext {
             ));
         }
 
+        // Only add Merge to list of forks if it's enabled
+        // Note: `merge_fork_epoch == None` implies merge hasn't been activated yet on the config.
+        if spec.merge_fork_epoch.is_some() {
+            fork_to_digest.push((
+                ForkName::Merge,
+                ChainSpec::compute_fork_digest(spec.merge_fork_version, genesis_validators_root),
+            ));
+        }
+
         let fork_to_digest: HashMap<ForkName, [u8; 4]> = fork_to_digest.into_iter().collect();
 
         let digest_to_fork = fork_to_digest
diff --git a/consensus/types/src/fork_name.rs b/consensus/types/src/fork_name.rs
index 85ba35e39..faf6c04de 100644
--- a/consensus/types/src/fork_name.rs
+++ b/consensus/types/src/fork_name.rs
@@ -10,6 +10,7 @@ use std::str::FromStr;
 pub enum ForkName {
     Base,
     Altair,
+    Merge,
 }
 
 impl ForkName {
@@ -24,10 +25,17 @@ impl ForkName {
         match self {
             ForkName::Base => {
                 spec.altair_fork_epoch = None;
+                spec.merge_fork_epoch = None;
                 spec
             }
             ForkName::Altair => {
                 spec.altair_fork_epoch = Some(Epoch::new(0));
+                spec.merge_fork_epoch = None;
+                spec
+            }
+            ForkName::Merge => {
+                spec.altair_fork_epoch = None;
+                spec.merge_fork_epoch = Some(Epoch::new(0));
                 spec
             }
         }
@@ -40,6 +48,7 @@ impl ForkName {
         match self {
             ForkName::Base => None,
             ForkName::Altair => Some(ForkName::Base),
+            ForkName::Merge => Some(ForkName::Altair),
         }
     }
 
@@ -49,7 +58,8 @@ impl ForkName {
     pub fn next_fork(self) -> Option<ForkName> {
         match self {
             ForkName::Base => Some(ForkName::Altair),
-            ForkName::Altair => None,
+            ForkName::Altair => Some(ForkName::Merge),
+            ForkName::Merge => None,
         }
     }
 }
@@ -98,6 +108,7 @@ impl FromStr for ForkName {
         Ok(match fork_name.to_lowercase().as_ref() {
             "phase0" | "base" => ForkName::Base,
             "altair" => ForkName::Altair,
+            "merge" => ForkName::Merge,
             _ => return Err(()),
         })
     }
@@ -108,6 +119,7 @@ impl Display for ForkName {
         match self {
             ForkName::Base => "phase0".fmt(f),
             ForkName::Altair => "altair".fmt(f),
+            ForkName::Merge => "merge".fmt(f),
         }
     }
 }
@@ -139,7 +151,7 @@ mod test {
 
     #[test]
     fn previous_and_next_fork_consistent() {
-        assert_eq!(ForkName::Altair.next_fork(), None);
+        assert_eq!(ForkName::Merge.next_fork(), None);
         assert_eq!(ForkName::Base.previous_fork(), None);
 
         for (prev_fork, fork) in ForkName::list_all().into_iter().tuple_windows() {
diff --git a/consensus/types/src/lib.rs b/consensus/types/src/lib.rs
index 403544f00..9ccd52f7b 100644
--- a/consensus/types/src/lib.rs
+++ b/consensus/types/src/lib.rs
@@ -37,6 +37,8 @@ pub mod deposit_message;
 pub mod enr_fork_id;
 pub mod eth1_data;
 pub mod eth_spec;
+pub mod execution_payload;
+pub mod execution_payload_header;
 pub mod fork;
 pub mod fork_data;
 pub mod fork_name;
@@ -45,6 +47,7 @@ pub mod graffiti;
 pub mod historical_batch;
 pub mod indexed_attestation;
 pub mod pending_attestation;
+pub mod pow_block;
 pub mod proposer_slashing;
 pub mod relative_epoch;
 pub mod selection_proof;
@@ -90,11 +93,12 @@ pub use crate::attestation_data::AttestationData;
 pub use crate::attestation_duty::AttestationDuty;
 pub use crate::attester_slashing::AttesterSlashing;
 pub use crate::beacon_block::{
-    BeaconBlock, BeaconBlockAltair, BeaconBlockBase, BeaconBlockRef, BeaconBlockRefMut,
+    BeaconBlock, BeaconBlockAltair, BeaconBlockBase, BeaconBlockMerge, BeaconBlockRef,
+    BeaconBlockRefMut,
 };
 pub use crate::beacon_block_body::{
-    BeaconBlockBody, BeaconBlockBodyAltair, BeaconBlockBodyBase, BeaconBlockBodyRef,
-    BeaconBlockBodyRefMut,
+    BeaconBlockBody, BeaconBlockBodyAltair, BeaconBlockBodyBase, BeaconBlockBodyMerge,
+    BeaconBlockBodyRef, BeaconBlockBodyRefMut,
 };
 pub use crate::beacon_block_header::BeaconBlockHeader;
 pub use crate::beacon_committee::{BeaconCommittee, OwnedBeaconCommittee};
@@ -109,6 +113,8 @@ pub use crate::deposit_message::DepositMessage;
 pub use crate::enr_fork_id::EnrForkId;
 pub use crate::eth1_data::Eth1Data;
 pub use crate::eth_spec::EthSpecId;
+pub use crate::execution_payload::ExecutionPayload;
+pub use crate::execution_payload_header::ExecutionPayloadHeader;
 pub use crate::fork::Fork;
 pub use crate::fork_context::ForkContext;
 pub use crate::fork_data::ForkData;
@@ -120,6 +126,7 @@ pub use crate::indexed_attestation::IndexedAttestation;
 pub use crate::participation_flags::ParticipationFlags;
 pub use crate::participation_list::ParticipationList;
 pub use crate::pending_attestation::PendingAttestation;
+pub use crate::pow_block::PowBlock;
 pub use crate::preset::{AltairPreset, BasePreset};
 pub use crate::proposer_slashing::ProposerSlashing;
 pub use crate::relative_epoch::{Error as RelativeEpochError, RelativeEpoch};
@@ -128,6 +135,7 @@ pub use crate::shuffling_id::AttestationShufflingId;
 pub use crate::signed_aggregate_and_proof::SignedAggregateAndProof;
 pub use crate::signed_beacon_block::{
     SignedBeaconBlock, SignedBeaconBlockAltair, SignedBeaconBlockBase, SignedBeaconBlockHash,
+    SignedBeaconBlockMerge,
 };
 pub use crate::signed_beacon_block_header::SignedBeaconBlockHeader;
 pub use crate::signed_contribution_and_proof::SignedContributionAndProof;
@@ -150,6 +158,7 @@ pub use crate::voluntary_exit::VoluntaryExit;
 
 pub type CommitteeIndex = u64;
 pub type Hash256 = H256;
+pub type Uint256 = ethereum_types::U256;
 pub type Address = H160;
 pub type ForkVersion = [u8; 4];
 
diff --git a/consensus/types/src/pow_block.rs b/consensus/types/src/pow_block.rs
new file mode 100644
index 000000000..056459af1
--- /dev/null
+++ b/consensus/types/src/pow_block.rs
@@ -0,0 +1,13 @@
+use crate::*;
+
+#[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
+#[derive(Default, Debug, PartialEq, Clone)]
+pub struct PowBlock {
+    pub block_hash: Hash256,
+    pub parent_hash: Hash256,
+    pub total_difficulty: Uint256,
+    pub difficulty: Uint256,
+    // needed to unify with other parts of codebase
+    pub timestamp: u64,
+    pub block_number: u64,
+}
diff --git a/consensus/types/src/signed_beacon_block.rs b/consensus/types/src/signed_beacon_block.rs
index a9d6f1d98..383805f97 100644
--- a/consensus/types/src/signed_beacon_block.rs
+++ b/consensus/types/src/signed_beacon_block.rs
@@ -37,7 +37,7 @@ impl From<SignedBeaconBlockHash> for Hash256 {
 
 /// A `BeaconBlock` and a signature from its proposer.
 #[superstruct(
-    variants(Base, Altair),
+    variants(Base, Altair, Merge),
     variant_attributes(
         derive(
             Debug,
@@ -64,6 +64,8 @@ pub struct SignedBeaconBlock<E: EthSpec> {
     pub message: BeaconBlockBase<E>,
     #[superstruct(only(Altair), partial_getter(rename = "message_altair"))]
     pub message: BeaconBlockAltair<E>,
+    #[superstruct(only(Merge), partial_getter(rename = "message_merge"))]
+    pub message: BeaconBlockMerge<E>,
     pub signature: Signature,
 }
 
@@ -116,6 +118,9 @@ impl<E: EthSpec> SignedBeaconBlock<E> {
             BeaconBlock::Altair(message) => {
                 SignedBeaconBlock::Altair(SignedBeaconBlockAltair { message, signature })
             }
+            BeaconBlock::Merge(message) => {
+                SignedBeaconBlock::Merge(SignedBeaconBlockMerge { message, signature })
+            }
         }
     }
 
@@ -129,6 +134,7 @@ impl<E: EthSpec> SignedBeaconBlock<E> {
             SignedBeaconBlock::Altair(block) => {
                 (BeaconBlock::Altair(block.message), block.signature)
             }
+            SignedBeaconBlock::Merge(block) => (BeaconBlock::Merge(block.message), block.signature),
         }
     }
 
@@ -137,6 +143,7 @@ impl<E: EthSpec> SignedBeaconBlock<E> {
         match self {
             SignedBeaconBlock::Base(inner) => BeaconBlockRef::Base(&inner.message),
             SignedBeaconBlock::Altair(inner) => BeaconBlockRef::Altair(&inner.message),
+            SignedBeaconBlock::Merge(inner) => BeaconBlockRef::Merge(&inner.message),
         }
     }
 
@@ -145,6 +152,7 @@ impl<E: EthSpec> SignedBeaconBlock<E> {
         match self {
             SignedBeaconBlock::Base(inner) => BeaconBlockRefMut::Base(&mut inner.message),
             SignedBeaconBlock::Altair(inner) => BeaconBlockRefMut::Altair(&mut inner.message),
+            SignedBeaconBlock::Merge(inner) => BeaconBlockRefMut::Merge(&mut inner.message),
         }
     }
 
diff --git a/consensus/types/src/test_utils/test_random.rs b/consensus/types/src/test_utils/test_random.rs
index bafbdca5f..064b57f42 100644
--- a/consensus/types/src/test_utils/test_random.rs
+++ b/consensus/types/src/test_utils/test_random.rs
@@ -14,6 +14,7 @@ mod public_key_bytes;
 mod secret_key;
 mod signature;
 mod signature_bytes;
+mod uint256;
 
 pub fn test_random_instance<T: TestRandom>() -> T {
     let mut rng = XorShiftRng::from_seed([0x42; 16]);
diff --git a/consensus/types/src/test_utils/test_random/hash256.rs b/consensus/types/src/test_utils/test_random/hash256.rs
index 8733f7de2..a74cc6b3d 100644
--- a/consensus/types/src/test_utils/test_random/hash256.rs
+++ b/consensus/types/src/test_utils/test_random/hash256.rs
@@ -1,10 +1,10 @@
 use super::*;
-use crate::Hash256;
+use crate::Uint256;
 
-impl TestRandom for Hash256 {
+impl TestRandom for Uint256 {
     fn random_for_test(rng: &mut impl RngCore) -> Self {
-        let mut key_bytes = vec![0; 32];
+        let mut key_bytes = [0; 32];
         rng.fill_bytes(&mut key_bytes);
-        Hash256::from_slice(&key_bytes[..])
+        Self::from_little_endian(&key_bytes[..])
     }
 }
diff --git a/consensus/types/src/test_utils/test_random/uint256.rs b/consensus/types/src/test_utils/test_random/uint256.rs
new file mode 100644
index 000000000..8733f7de2
--- /dev/null
+++ b/consensus/types/src/test_utils/test_random/uint256.rs
@@ -0,0 +1,10 @@
+use super::*;
+use crate::Hash256;
+
+impl TestRandom for Hash256 {
+    fn random_for_test(rng: &mut impl RngCore) -> Self {
+        let mut key_bytes = vec![0; 32];
+        rng.fill_bytes(&mut key_bytes);
+        Hash256::from_slice(&key_bytes[..])
+    }
+}
diff --git a/testing/ef_tests/src/cases/common.rs b/testing/ef_tests/src/cases/common.rs
index 175ad113b..ade8711cd 100644
--- a/testing/ef_tests/src/cases/common.rs
+++ b/testing/ef_tests/src/cases/common.rs
@@ -77,5 +77,6 @@ pub fn previous_fork(fork_name: ForkName) -> ForkName {
     match fork_name {
         ForkName::Base => ForkName::Base,
         ForkName::Altair => ForkName::Base,
+        ForkName::Merge => ForkName::Altair, // TODO: Check this when tests are released..
     }
 }
diff --git a/testing/ef_tests/src/cases/epoch_processing.rs b/testing/ef_tests/src/cases/epoch_processing.rs
index 56e6c9b7b..fa27a94ce 100644
--- a/testing/ef_tests/src/cases/epoch_processing.rs
+++ b/testing/ef_tests/src/cases/epoch_processing.rs
@@ -94,10 +94,12 @@ impl<E: EthSpec> EpochTransition<E> for JustificationAndFinalization {
                     spec,
                 )
             }
-            BeaconState::Altair(_) => altair::process_justification_and_finalization(
-                state,
-                &altair::ParticipationCache::new(state, spec).unwrap(),
-            ),
+            BeaconState::Altair(_) | BeaconState::Merge(_) => {
+                altair::process_justification_and_finalization(
+                    state,
+                    &altair::ParticipationCache::new(state, spec).unwrap(),
+                )
+            }
         }
     }
 }
@@ -110,11 +112,13 @@ impl<E: EthSpec> EpochTransition<E> for RewardsAndPenalties {
                 validator_statuses.process_attestations(state)?;
                 base::process_rewards_and_penalties(state, &mut validator_statuses, spec)
             }
-            BeaconState::Altair(_) => altair::process_rewards_and_penalties(
-                state,
-                &altair::ParticipationCache::new(state, spec).unwrap(),
-                spec,
-            ),
+            BeaconState::Altair(_) | BeaconState::Merge(_) => {
+                altair::process_rewards_and_penalties(
+                    state,
+                    &altair::ParticipationCache::new(state, spec).unwrap(),
+                    spec,
+                )
+            }
         }
     }
 }
@@ -138,7 +142,7 @@ impl<E: EthSpec> EpochTransition<E> for Slashings {
                     spec,
                 )?;
             }
-            BeaconState::Altair(_) => {
+            BeaconState::Altair(_) | BeaconState::Merge(_) => {
                 process_slashings(
                     state,
                     altair::ParticipationCache::new(state, spec)
@@ -197,7 +201,9 @@ impl<E: EthSpec> EpochTransition<E> for SyncCommitteeUpdates {
     fn run(state: &mut BeaconState<E>, spec: &ChainSpec) -> Result<(), EpochProcessingError> {
         match state {
             BeaconState::Base(_) => Ok(()),
-            BeaconState::Altair(_) => altair::process_sync_committee_updates(state, spec),
+            BeaconState::Altair(_) | BeaconState::Merge(_) => {
+                altair::process_sync_committee_updates(state, spec)
+            }
         }
     }
 }
@@ -206,7 +212,7 @@ impl<E: EthSpec> EpochTransition<E> for InactivityUpdates {
     fn run(state: &mut BeaconState<E>, spec: &ChainSpec) -> Result<(), EpochProcessingError> {
         match state {
             BeaconState::Base(_) => Ok(()),
-            BeaconState::Altair(_) => altair::process_inactivity_updates(
+            BeaconState::Altair(_) | BeaconState::Merge(_) => altair::process_inactivity_updates(
                 state,
                 &altair::ParticipationCache::new(state, spec).unwrap(),
                 spec,
@@ -219,7 +225,9 @@ impl<E: EthSpec> EpochTransition<E> for ParticipationFlagUpdates {
     fn run(state: &mut BeaconState<E>, _: &ChainSpec) -> Result<(), EpochProcessingError> {
         match state {
             BeaconState::Base(_) => Ok(()),
-            BeaconState::Altair(_) => altair::process_participation_flag_updates(state),
+            BeaconState::Altair(_) | BeaconState::Merge(_) => {
+                altair::process_participation_flag_updates(state)
+            }
         }
     }
 }
@@ -267,7 +275,7 @@ impl<E: EthSpec, T: EpochTransition<E>> Case for EpochProcessing<E, T> {
                     && T::name() != "inactivity_updates"
                     && T::name() != "participation_flag_updates"
             }
-            ForkName::Altair => true,
+            ForkName::Altair | ForkName::Merge => true, // TODO: revisit when tests are out
         }
     }
 
diff --git a/testing/ef_tests/src/cases/operations.rs b/testing/ef_tests/src/cases/operations.rs
index 293195662..360abbb67 100644
--- a/testing/ef_tests/src/cases/operations.rs
+++ b/testing/ef_tests/src/cases/operations.rs
@@ -72,7 +72,7 @@ impl<E: EthSpec> Operation<E> for Attestation<E> {
             BeaconState::Base(_) => {
                 base::process_attestations(state, &[self.clone()], VerifySignatures::True, spec)
             }
-            BeaconState::Altair(_) => altair::process_attestation(
+            BeaconState::Altair(_) | BeaconState::Merge(_) => altair::process_attestation(
                 state,
                 self,
                 0,
diff --git a/testing/ef_tests/src/cases/transition.rs b/testing/ef_tests/src/cases/transition.rs
index d41a52d52..861e65d3d 100644
--- a/testing/ef_tests/src/cases/transition.rs
+++ b/testing/ef_tests/src/cases/transition.rs
@@ -37,6 +37,9 @@ impl<E: EthSpec> LoadCase for TransitionTest<E> {
             ForkName::Altair => {
                 spec.altair_fork_epoch = Some(metadata.fork_epoch);
             }
+            ForkName::Merge => {
+                spec.merge_fork_epoch = Some(metadata.fork_epoch);
+            }
         }
 
         // Load blocks
diff --git a/testing/ef_tests/src/handler.rs b/testing/ef_tests/src/handler.rs
index 11bda8f9f..e42098342 100644
--- a/testing/ef_tests/src/handler.rs
+++ b/testing/ef_tests/src/handler.rs
@@ -34,6 +34,7 @@ pub trait Handler {
         let fork_name_str = match fork_name {
             ForkName::Base => "phase0",
             ForkName::Altair => "altair",
+            ForkName::Merge => "merge", // TODO: check this
         };
 
         let handler_path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))