diff --git a/eth/api.go b/eth/api.go
index f5214fc379a4..35ab327ab043 100644
--- a/eth/api.go
+++ b/eth/api.go
@@ -71,6 +71,15 @@ func (api *PublicEthereumAPI) Hashrate() hexutil.Uint64 {
 	return hexutil.Uint64(api.e.Miner().HashRate())
 }
 
+// ChainId is the EIP-155 replay-protection chain id for the current ethereum chain config.
+func (api *PublicEthereumAPI) ChainId() hexutil.Uint {
+	chainID := new(big.Int)
+	if config := api.e.chainConfig; config.IsEIP155(api.e.blockchain.CurrentBlock().Number()) {
+		chainID = config.ChainId
+	}
+	return hexutil.Uint(chainID)
+}
+
 // PublicMinerAPI provides an API to control the miner.
 // It offers only methods that operate on data that pose no security risk when it is publicly accessible.
 type PublicMinerAPI struct {
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index bf1db88196b7..d6c2adcc57da 100644
--- a/internal/web3ext/web3ext.go
+++ b/internal/web3ext/web3ext.go
@@ -360,6 +360,11 @@ web3._extend({
 	property: 'eth',
 	methods:
 	[
+		new web3._extend.Method({
+			name: 'chainId',
+			call: 'eth_chainId',
+			params: 0
+		}),
 		new web3._extend.Method({
 			name: 'sign',
 			call: 'eth_sign',