diff --git a/README.md b/README.md
index f830cc3..c78ef4d 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,7 @@ Patch locales functions to koa app.
   - {String} defaultLocale: default locale. Optional, default is `en-US`.
   - {String} queryField: locale field name on query. Optional, default is `locale`.
   - {String} cookieField: locale field name on cookie. Optional, default is `locale`.
+  - {Object} localeAlias: locale cookie value map. Optional, default is {}.
   - {String|Number} cookieMaxAge: set locale cookie value max age. Optional, default is `1y`, expired after one year.
 
 ```js
diff --git a/index.js b/index.js
index f6dcfb5..892c0b6 100644
--- a/index.js
+++ b/index.js
@@ -24,6 +24,7 @@ const DEFAULT_OPTIONS = {
   defaultLocale: 'en-US',
   queryField: 'locale',
   cookieField: 'locale',
+  localeAlias: {},
   cookieMaxAge: '1y',
   dir: undefined,
   dirs: [path.join(process.cwd(), 'locales')],
@@ -35,6 +36,7 @@ module.exports = function (app, options) {
   const defaultLocale = formatLocale(options.defaultLocale);
   const queryField = options.queryField;
   const cookieField = options.cookieField;
+  const localeAlias = options.localeAlias;
   const cookieMaxAge = ms(options.cookieMaxAge);
   const localeDir = options.dir;
   const localeDirs = options.dirs;
@@ -172,6 +174,9 @@ module.exports = function (app, options) {
       }
     }
 
+    // cookie alias
+    if (locale in localeAlias) locale = localeAlias[locale];
+
     locale = formatLocale(locale);
 
     // validate locale
diff --git a/test/index.test.js b/test/index.test.js
index cb664d4..310e668 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -66,6 +66,13 @@ describe('koa-locales.test.js', function () {
     const app = createApp({
       dirs: [__dirname + '/locales', __dirname + '/other-locales'],
     });
+    const cookieFieldMapApp = createApp({
+      dirs: [__dirname + '/locales', __dirname + '/other-locales'],
+      localeAlias: {
+        'en': 'en-US',
+        'de-de': 'de',
+      },
+    });
 
     it('should use default locale: en-US', function (done) {
       request(app.callback())
@@ -193,6 +200,31 @@ describe('koa-locales.test.js', function () {
         .expect('Set-Cookie', /^locale=en\-us; path=\/; expires=\w+/)
         .expect(200, done);
       });
+
+      it('should use localeAlias', function (done) {
+        request(cookieFieldMapApp.callback())
+        .get('/?locale=de-de')
+        .expect({
+          email: 'Emailde',
+          hello: 'Hallo fengmk2, wie geht es dir heute?',
+          message: 'Hallo fengmk2, wie geht es dir heute? Wie war dein 18.',
+          empty: '',
+          notexists_key: 'key not exists',
+          empty_string: '',
+          empty_value: 'emptyValue',
+          novalue: 'key %s ok',
+          arguments3: '1 2 3',
+          arguments4: '1 2 3 4',
+          arguments5: '1 2 3 4 5',
+          arguments6: '1 2 3 4 5. 6',
+          values: 'foo bar foo bar {2} {100}',
+          object: 'foo bar foo bar {z}',
+          'gender': 'model.user.fields.gender',
+          'name': 'model.user.fields.name',
+        })
+        .expect('Set-Cookie', /^locale=de; path=\/; expires=\w+/)
+        .expect(200, done);
+      });
     });
 
     describe('cookie.locale', function () {