diff --git a/.changeset/clever-days-occur.md b/.changeset/clever-days-occur.md
new file mode 100644
index 0000000000..d07fe5abf0
--- /dev/null
+++ b/.changeset/clever-days-occur.md
@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Updated World Chain (Mainnet and Testnet) and Unichain Sepolia chain definitions
diff --git a/src/chains/definitions/unichainSepolia.ts b/src/chains/definitions/unichainSepolia.ts
index 49797bc65b..867dca6e51 100644
--- a/src/chains/definitions/unichainSepolia.ts
+++ b/src/chains/definitions/unichainSepolia.ts
@@ -1,8 +1,10 @@
+import { chainConfig } from '../../op-stack/chainConfig.js'
 import { defineChain } from '../../utils/chain/defineChain.js'
 
 const sourceId = 11_155_111 // sepolia
 
 export const unichainSepolia = /*#__PURE__*/ defineChain({
+  ...chainConfig,
   id: 1301,
   name: 'Unichain Sepolia',
   nativeCurrency: {
@@ -23,10 +25,26 @@ export const unichainSepolia = /*#__PURE__*/ defineChain({
     },
   },
   contracts: {
+    ...chainConfig.contracts,
     multicall3: {
       address: '0xca11bde05977b3631167028862be2a173976ca11',
       blockCreated: 0,
     },
+    portal: {
+      [sourceId]: {
+        address: '0x0d83dab629f0e0F9d36c0Cbc89B69a489f0751bD',
+      },
+    },
+    l1StandardBridge: {
+      [sourceId]: {
+        address: '0xea58fcA6849d79EAd1f26608855c2D6407d54Ce2',
+      },
+    },
+    disputeGameFactory: {
+      [sourceId]: {
+        address: '0xeff73e5aa3B9AEC32c659Aa3E00444d20a84394b',
+      },
+    },
   },
   testnet: true,
   sourceId,
diff --git a/src/chains/definitions/worldchain.ts b/src/chains/definitions/worldchain.ts
index 3840973906..b4079b37de 100644
--- a/src/chains/definitions/worldchain.ts
+++ b/src/chains/definitions/worldchain.ts
@@ -4,6 +4,7 @@ import { defineChain } from '../../utils/chain/defineChain.js'
 const sourceId = 1 // mainnet
 
 export const worldchain = /*#__PURE__*/ defineChain({
+  ...chainConfig,
   id: 480,
   name: 'World Chain',
   network: 'worldchain',
diff --git a/src/chains/definitions/worldchainSepolia.ts b/src/chains/definitions/worldchainSepolia.ts
index c333effe4c..6a1a40ad6d 100644
--- a/src/chains/definitions/worldchainSepolia.ts
+++ b/src/chains/definitions/worldchainSepolia.ts
@@ -4,6 +4,7 @@ import { defineChain } from '../../utils/chain/defineChain.js'
 const sourceId = 11_155_111 // sepolia
 
 export const worldchainSepolia = /*#__PURE__*/ defineChain({
+  ...chainConfig,
   id: 4801,
   name: 'World Chain Sepolia',
   network: 'worldchain-sepolia',
diff --git a/src/op-stack/chains.ts b/src/op-stack/chains.ts
index 66b95e5010..1d58f28872 100644
--- a/src/op-stack/chains.ts
+++ b/src/op-stack/chains.ts
@@ -16,6 +16,7 @@ export { shape } from '../chains/definitions/shape.js'
 export { snax } from '../chains/definitions/snax.js'
 export { snaxTestnet } from '../chains/definitions/snaxTestnet.js'
 export { soneiumMinato } from '../chains/definitions/soneiumMinato.js'
+export { unichainSepolia } from '../chains/definitions/unichainSepolia.js'
 export { worldchain } from '../chains/definitions/worldchain.js'
 export { worldchainSepolia } from '../chains/definitions/worldchainSepolia.js'
 export { zora } from '../chains/definitions/zora.js'