diff --git a/app/assets/javascripts/components/containers/mastodon.jsx b/app/assets/javascripts/components/containers/mastodon.jsx
index fea8b15949..d48bb2ba98 100644
--- a/app/assets/javascripts/components/containers/mastodon.jsx
+++ b/app/assets/javascripts/components/containers/mastodon.jsx
@@ -49,6 +49,7 @@ import uk from 'react-intl/locale-data/uk';
 import fi from 'react-intl/locale-data/fi';
 import eo from 'react-intl/locale-data/eo';
 import ru from 'react-intl/locale-data/ru';
+import ja from 'react-intl/locale-data/ja';
 
 import getMessagesForLocale from '../locales';
 import { hydrateStore } from '../actions/store';
@@ -63,7 +64,7 @@ const browserHistory = useRouterHistory(createBrowserHistory)({
 });
 
 
-addLocaleData([...en, ...de, ...es, ...fr, ...pt, ...hu, ...uk, ...fi, ...eo, ...ru]);
+addLocaleData([...en, ...de, ...es, ...fr, ...pt, ...hu, ...uk, ...fi, ...eo, ...ru, ...ja]);
 
 
 const Mastodon = React.createClass({
diff --git a/app/assets/javascripts/components/locales/index.jsx b/app/assets/javascripts/components/locales/index.jsx
index f9e1fe5bd4..da85240b7e 100644
--- a/app/assets/javascripts/components/locales/index.jsx
+++ b/app/assets/javascripts/components/locales/index.jsx
@@ -8,6 +8,7 @@ import uk from './uk';
 import fi from './fi';
 import eo from './eo';
 import ru from './ru';
+import ja from './ja';
 
 
 const locales = {
@@ -20,7 +21,8 @@ const locales = {
   uk,
   fi,
   eo,
-  ru
+  ru,
+  ja
 
 };
 
diff --git a/app/helpers/settings_helper.rb b/app/helpers/settings_helper.rb
index 327ca4e989..8a94df5f4d 100644
--- a/app/helpers/settings_helper.rb
+++ b/app/helpers/settings_helper.rb
@@ -13,6 +13,7 @@ module SettingsHelper
     'zh-CN': '简体中文',
     fi: 'Suomi',
     ru: 'Русский',
+    ja: '日本語',
 
   }.freeze
 
diff --git a/config/application.rb b/config/application.rb
index dc937ca0eb..a3991639c5 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -25,7 +25,7 @@ module Mastodon
     # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
     # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
 
-    config.i18n.available_locales = [:en, :de, :es, :pt, :fr, :hu, :uk, 'zh-CN', :fi, :eo, :ru]
+    config.i18n.available_locales = [:en, :de, :es, :pt, :fr, :hu, :uk, 'zh-CN', :fi, :eo, :ru, :ja]
 
     config.i18n.default_locale    = :en