diff --git a/.changeset/gold-points-tan.md b/.changeset/gold-points-tan.md
new file mode 100644
index 0000000000..2976ae1068
--- /dev/null
+++ b/.changeset/gold-points-tan.md
@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+**OP Stack:** Added `proofSubmitter` parameter to `finalizeWithdrawal` for finalizing withdrawals under a different account.
diff --git a/site/pages/op-stack/actions/estimateFinalizeWithdrawalGas.md b/site/pages/op-stack/actions/estimateFinalizeWithdrawalGas.md
index 13de3d7575..49e15ba1dc 100644
--- a/site/pages/op-stack/actions/estimateFinalizeWithdrawalGas.md
+++ b/site/pages/op-stack/actions/estimateFinalizeWithdrawalGas.md
@@ -101,6 +101,23 @@ const hash = await client.estimateFinalizeWithdrawalGas({
 })
 ```
 
+### proofSubmitter (optional)
+
+- **Type:** `Address`
+
+The address of the proof submitter to use when finalizing the withdrawal. No-op when the OptimismPortal contract version is less than v3.
+
+If unspecified, the sending account is the proof submitter.
+
+```ts
+const hash = await client.finalizeWithdrawal({
+  account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266',
+  proofSubmitter: '0xD15F47c16BD277ff2dee6a0bD4e418165231CB69', // [!code focus]
+  withdrawal: { /* ... */ },
+  targetChain: optimism,
+})
+```
+
 ### maxFeePerGas (optional)
 
 - **Type:** `bigint`
diff --git a/site/pages/op-stack/actions/finalizeWithdrawal.md b/site/pages/op-stack/actions/finalizeWithdrawal.md
index d4fd6e39e9..4bb2596741 100644
--- a/site/pages/op-stack/actions/finalizeWithdrawal.md
+++ b/site/pages/op-stack/actions/finalizeWithdrawal.md
@@ -7,7 +7,9 @@ description: Finalizes a withdrawal that occurred on an L2.
 
 Finalizes a withdrawal that occurred on an L2. Used in the Withdrawal flow.
 
-Internally performs a contract write to the [`finalizeWithdrawalTransaction` function](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L1/OptimismPortal.sol#L272) on the [Optimism Portal contract](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L1/OptimismPortal.sol).
+Internally performs a contract write to the [`finalizeWithdrawalTransaction` function](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L1/OptimismPortal2.sol#L383) on the [Optimism Portal contract](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L1/OptimismPortal2.sol).
+
+If the proof submitter is specified and the OptimismPortal contract version is v3 or greater, the [`finalizeWithdrawalTransactionExternalProof` function](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L1/OptimismPortal2.sol#L390) function will be used to finalize the withdrawal with the provided address as the proof submitter.
 
 ## Usage
 
@@ -177,6 +179,23 @@ const hash = await client.finalizeWithdrawal({
 })
 ```
 
+### proofSubmitter (optional)
+
+- **Type:** `Address`
+
+The address of the proof submitter to use when finalizing the withdrawal. No-op when the OptimismPortal contract version is less than v3.
+
+If unspecified, the sending account is the proof submitter.
+
+```ts
+const hash = await client.finalizeWithdrawal({
+  account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266',
+  proofSubmitter: '0xD15F47c16BD277ff2dee6a0bD4e418165231CB69', // [!code focus]
+  withdrawal: { /* ... */ },
+  targetChain: optimism,
+})
+```
+
 ### maxFeePerGas (optional)
 
 - **Type:** `bigint`
diff --git a/src/op-stack/actions/estimateFinalizeWithdrawalGas.test.ts b/src/op-stack/actions/estimateFinalizeWithdrawalGas.test.ts
index 36f5e253b6..ee5c71f0b6 100644
--- a/src/op-stack/actions/estimateFinalizeWithdrawalGas.test.ts
+++ b/src/op-stack/actions/estimateFinalizeWithdrawalGas.test.ts
@@ -35,3 +35,33 @@ test('default', async () => {
   })
   expect(gas).toBeDefined()
 })
+
+test('args: proof submitter', async () => {
+  // TODO: migrate the rest of the test suite to a block with fault proofs
+  // Sample withdrawal with fault proofs: https://optimistic.etherscan.io/tx/0x039d2fdf3161910cb667ed599a0a899314bd5041797b6707ba312792b6d43b5c
+  await reset(client, {
+    blockNumber: 21165285n,
+    jsonRpcUrl: anvilMainnet.forkUrl,
+  })
+
+  const proofSubmitter = '0xD15F47c16BD277ff2dee6a0bD4e418165231CB69'
+  const withdrawal = {
+    nonce:
+      1766847064778384329583297500742918515827483896875618958121606201292641117n,
+    sender: '0x4200000000000000000000000000000000000007',
+    target: '0x25ace71c97B33Cc4729CF772ae268934F7ab5fA1',
+    value: 0n,
+    gasLimit: 3334219n,
+    data: '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',
+    withdrawalHash:
+      '0xD55C5BA792D04BC45656D5115F98A4AE446F66C857A41B6666C045023B7EBDB7',
+  } as const
+
+  const gas = await estimateFinalizeWithdrawalGas(client, {
+    account: accounts[0].address,
+    targetChain: optimism,
+    withdrawal,
+    proofSubmitter, // on behalf of the proof submittor
+  })
+  expect(gas).toBeDefined()
+})
diff --git a/src/op-stack/actions/estimateFinalizeWithdrawalGas.ts b/src/op-stack/actions/estimateFinalizeWithdrawalGas.ts
index a5590b2064..ba4f2bde46 100644
--- a/src/op-stack/actions/estimateFinalizeWithdrawalGas.ts
+++ b/src/op-stack/actions/estimateFinalizeWithdrawalGas.ts
@@ -15,7 +15,7 @@ import type {
 } from '../../types/chain.js'
 import type { UnionEvaluate, UnionOmit } from '../../types/utils.js'
 import type { FormattedTransactionRequest } from '../../utils/formatters/transactionRequest.js'
-import { portalAbi } from '../abis.js'
+import { portal2Abi, portalAbi } from '../abis.js'
 import type { GetContractAddressParameter } from '../types/contract.js'
 import type { Withdrawal } from '../types/withdrawal.js'
 
@@ -42,6 +42,11 @@ export type EstimateFinalizeWithdrawalGasParameters<
   GetContractAddressParameter<_derivedChain, 'portal'> & {
     /** Gas limit for transaction execution on the L2. */
     gas?: bigint | undefined
+    /**
+     * Finalize against a specific proof submitter.
+     * If unspecified, the sending account is the default.
+     */
+    proofSubmitter?: Address | null | undefined
     withdrawal: Withdrawal
   }
 export type EstimateFinalizeWithdrawalGasReturnType = bigint
@@ -93,6 +98,7 @@ export async function estimateFinalizeWithdrawalGas<
     maxFeePerGas,
     maxPriorityFeePerGas,
     nonce,
+    proofSubmitter,
     targetChain,
     withdrawal,
   } = parameters
@@ -103,12 +109,20 @@ export async function estimateFinalizeWithdrawalGas<
     return Object.values(targetChain!.contracts.portal)[0].address
   })()
 
+  const [functionName, args, abi] = proofSubmitter
+    ? [
+        'finalizeWithdrawalTransactionExternalProof',
+        [withdrawal, proofSubmitter],
+        portal2Abi,
+      ]
+    : ['finalizeWithdrawalTransaction', [withdrawal], portalAbi]
+
   const params = {
     account,
-    abi: portalAbi,
+    abi,
     address: portalAddress,
-    functionName: 'finalizeWithdrawalTransaction',
-    args: [withdrawal],
+    functionName,
+    args,
     gas,
     maxFeePerGas,
     maxPriorityFeePerGas,
@@ -117,9 +131,7 @@ export async function estimateFinalizeWithdrawalGas<
     // in `estimateContractGas` or `estimateGas`
     // @ts-ignore
     chain,
-  } satisfies EstimateContractGasParameters<
-    typeof portalAbi,
-    'finalizeWithdrawalTransaction'
-  >
+  } satisfies EstimateContractGasParameters
+
   return estimateContractGas(client, params as any)
 }
diff --git a/src/op-stack/actions/finalizeWithdrawal.test.ts b/src/op-stack/actions/finalizeWithdrawal.test.ts
index 884662a2b9..b8af4eee3d 100644
--- a/src/op-stack/actions/finalizeWithdrawal.test.ts
+++ b/src/op-stack/actions/finalizeWithdrawal.test.ts
@@ -111,6 +111,43 @@ test('args: portal address', async () => {
   expect(receipt.status).toEqual('success')
 })
 
+test('args: proof submitter', async () => {
+  // TODO: migrate the rest of the test suite to a block with fault proofs
+  // Sample withdrawal with fault proofs: https://optimistic.etherscan.io/tx/0x039d2fdf3161910cb667ed599a0a899314bd5041797b6707ba312792b6d43b5c
+  await reset(client, {
+    blockNumber: 21165285n,
+    jsonRpcUrl: anvilMainnet.forkUrl,
+  })
+
+  const proofSubmitter = '0xD15F47c16BD277ff2dee6a0bD4e418165231CB69'
+  const withdrawal = {
+    nonce:
+      1766847064778384329583297500742918515827483896875618958121606201292641117n,
+    sender: '0x4200000000000000000000000000000000000007',
+    target: '0x25ace71c97B33Cc4729CF772ae268934F7ab5fA1',
+    value: 0n,
+    gasLimit: 3334219n,
+    data: '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',
+    withdrawalHash:
+      '0xD55C5BA792D04BC45656D5115F98A4AE446F66C857A41B6666C045023B7EBDB7',
+  } as const
+
+  const hash = await finalizeWithdrawal(client, {
+    account: accounts[0].address,
+    targetChain: optimism,
+    withdrawal,
+    proofSubmitter, // on behalf of the proof submittor
+  })
+  expect(hash).toBeDefined()
+
+  await mine(client, { blocks: 1 })
+
+  const receipt = await getTransactionReceipt(client, {
+    hash,
+  })
+  expect(receipt.status).toEqual('success')
+})
+
 test('error: small gas', async () => {
   await expect(() =>
     finalizeWithdrawal(client, {
diff --git a/src/op-stack/actions/finalizeWithdrawal.ts b/src/op-stack/actions/finalizeWithdrawal.ts
index e8717005ee..e238a64195 100644
--- a/src/op-stack/actions/finalizeWithdrawal.ts
+++ b/src/op-stack/actions/finalizeWithdrawal.ts
@@ -16,7 +16,7 @@ import type {
 import type { Hash } from '../../types/misc.js'
 import type { UnionEvaluate, UnionOmit } from '../../types/utils.js'
 import type { FormattedTransactionRequest } from '../../utils/formatters/transactionRequest.js'
-import { portalAbi } from '../abis.js'
+import { portal2Abi, portalAbi } from '../abis.js'
 import type { GetContractAddressParameter } from '../types/contract.js'
 import type { Withdrawal } from '../types/withdrawal.js'
 import {
@@ -51,6 +51,11 @@ export type FinalizeWithdrawalParameters<
      * `null` to skip gas estimation & defer calculation to signer.
      */
     gas?: bigint | null | undefined
+    /**
+     * Finalize against a provided proof submitter.
+     * If unspecified, the sending account is the default.
+     */
+    proofSubmitter?: Address | null | undefined
     withdrawal: Withdrawal
   }
 export type FinalizeWithdrawalReturnType = Hash
@@ -98,6 +103,7 @@ export async function finalizeWithdrawal<
     maxFeePerGas,
     maxPriorityFeePerGas,
     nonce,
+    proofSubmitter,
     targetChain,
     withdrawal,
   } = parameters
@@ -116,13 +122,21 @@ export async function finalizeWithdrawal<
         )
       : undefined
 
+  const [functionName, args, abi] = proofSubmitter
+    ? [
+        'finalizeWithdrawalTransactionExternalProof',
+        [withdrawal, proofSubmitter],
+        portal2Abi,
+      ]
+    : ['finalizeWithdrawalTransaction', [withdrawal], portalAbi]
+
   return writeContract(client, {
     account: account!,
-    abi: portalAbi,
+    abi,
     address: portalAddress,
     chain,
-    functionName: 'finalizeWithdrawalTransaction',
-    args: [withdrawal],
+    functionName,
+    args,
     gas: gas_,
     maxFeePerGas,
     maxPriorityFeePerGas,