diff --git a/src/common/mainWorldI18n/Client.js b/src/common/mainWorldI18n/Client.js
new file mode 100644
index 0000000..b1b8286
--- /dev/null
+++ b/src/common/mainWorldI18n/Client.js
@@ -0,0 +1,20 @@
+import MainWorldContentScriptBridgeClient from '../mainWorldContentScriptBridge/Client.js';
+
+import {kCSTarget, kMWTarget} from './consts.js';
+
+// Main World i18n client (used in scripts injected into the Main World (MW) to
+// use the chrome.i18n API).
+export default class MWI18nClient extends MainWorldContentScriptBridgeClient {
+  constructor(timeout) {
+    super(kCSTarget, kMWTarget, timeout);
+  }
+
+  async getMessage(messageName, substitutions, options) {
+    return this._sendRequest(
+        'getMessage', {messageName, substitutions, options});
+  }
+
+  async getUILanguage() {
+    return this._sendRequest('getUILanguage', {});
+  }
+}
diff --git a/src/common/mainWorldI18n/Server.js b/src/common/mainWorldI18n/Server.js
new file mode 100644
index 0000000..7299ee9
--- /dev/null
+++ b/src/common/mainWorldI18n/Server.js
@@ -0,0 +1,29 @@
+import MainWorldContentScriptBridgeServer from '../mainWorldContentScriptBridge/Server.js';
+
+import {kCSTarget, kMWTarget} from './consts.js';
+
+// Main World i18n server (used in content scripts to be able to serve the
+// chrome.i18n API to Main World (MW) scripts).
+export default class MWI18nServer extends MainWorldContentScriptBridgeServer {
+  constructor() {
+    super(kCSTarget, kMWTarget);
+    this.setUpHandler(this.handleMessage);
+  }
+
+  handleMessage(uuid, action, request) {
+    switch (action) {
+      case 'getMessage':
+        var response = chrome.i18n.getMessage(
+            request.messageName, request.substitutions, request.options);
+        this._respond(uuid, response);
+        return;
+
+      case 'getUILanguage':
+        this._respond(uuid, chrome.i18n.getUILanguage());
+        return;
+
+      default:
+        console.error(`[MWI18nServer] Invalid action received (${action})`);
+    }
+  }
+}
diff --git a/src/common/mainWorldI18n/consts.js b/src/common/mainWorldI18n/consts.js
new file mode 100644
index 0000000..d022bc2
--- /dev/null
+++ b/src/common/mainWorldI18n/consts.js
@@ -0,0 +1,2 @@
+export const kCSTarget = 'TWPT-I18n-CS';
+export const kMWTarget = 'TWPT-I18n-MW';