diff --git a/lib/site_setting_extension.rb b/lib/site_setting_extension.rb
index 8efee070324..4e525ff72a9 100644
--- a/lib/site_setting_extension.rb
+++ b/lib/site_setting_extension.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency 'site_settings/deprecated_settings'
 require_dependency 'site_settings/type_supervisor'
 require_dependency 'site_settings/defaults_provider'
@@ -5,12 +7,54 @@ require_dependency 'site_settings/db_provider'
 
 module SiteSettingExtension
   include SiteSettings::DeprecatedSettings
-  extend Forwardable
 
-  def_delegator :defaults, :site_locale, :default_locale
-  def_delegator :defaults, :site_locale=, :default_locale=
-  def_delegator :defaults, :has_setting?
-  def_delegators 'SiteSettings::TypeSupervisor', :types, :supported_types
+  # support default_locale being set via global settings
+  # this also adds support for testing the extension and global settings
+  # for site locale
+  def self.extended(klass)
+    if GlobalSetting.respond_to?(:default_locale) && GlobalSetting.default_locale.present?
+      klass.send :setup_shadowed_methods, :default_locale, GlobalSetting.default_locale
+    end
+  end
+
+  # we need a default here to support defaults per locale
+  def default_locale=(val)
+    val = val.to_s
+    raise Discourse::InvalidParameters.new(:value) unless LocaleSiteSetting.valid_value?(val)
+    if val != self.default_locale
+      add_override!(:default_locale, val)
+      refresh!
+      Discourse.request_refresh!
+    end
+  end
+
+  def default_locale?
+    true
+  end
+
+  # set up some sort of default so we can look stuff up
+  def default_locale
+    # note optimised cause this is called a lot so avoiding .presence which
+    # adds 2 method calls
+    locale = current[:default_locale]
+    if locale && !locale.blank?
+      locale
+    else
+      SiteSettings::DefaultsProvider::DEFAULT_LOCALE
+    end
+  end
+
+  def has_setting?(v)
+    defaults.has_setting?(v)
+  end
+
+  def supported_types
+    SiteSettings::TypeSupervisor.supported_types
+  end
+
+  def types
+    SiteSettings::TypeSupervisor.types
+  end
 
   def listen_for_changes=(val)
     @listen_for_changes = val
@@ -55,11 +99,11 @@ module SiteSettingExtension
   end
 
   def refresh_settings
-    @refresh_settings ||= []
+    @refresh_settings ||= [:default_locale]
   end
 
   def client_settings
-    @client_settings ||= []
+    @client_settings ||= [:default_locale]
   end
 
   def previews
@@ -73,13 +117,17 @@ module SiteSettingExtension
   def setting(name_arg, default = nil, opts = {})
     name = name_arg.to_sym
 
+    if name == :default_locale
+      raise ArgumentError.new("Other settings depend on default locale, you can not configure it like this")
+    end
+
     shadowed_val = nil
 
     mutex.synchronize do
       defaults.load_setting(
         name,
         default,
-        opts.extract!(*SiteSettings::DefaultsProvider::CONSUMED_OPTS)
+        opts.delete(:locale_default)
       )
 
       categories[name] = opts[:category] || :uncategorized
@@ -129,7 +177,7 @@ module SiteSettingExtension
 
   def settings_hash
     result = {}
-    defaults.each_key do |s|
+    defaults.all.keys.each do |s|
       result[s] = send(s).to_s
     end
     result
@@ -147,14 +195,28 @@ module SiteSettingExtension
 
   # Retrieve all settings
   def all_settings(include_hidden = false)
-    defaults
+
+    locale_setting_hash =
+    {
+      setting: 'default_locale',
+      default: SiteSettings::DefaultsProvider::DEFAULT_LOCALE,
+      category: 'required',
+      description: description('default_locale'),
+      type: SiteSetting.types[SiteSetting.types[:enum]],
+      preview: nil,
+      value: self.default_locale,
+      valid_values: LocaleSiteSetting.values,
+      translate_names: LocaleSiteSetting.translate_names?
+    }
+
+    defaults.all(default_locale)
       .reject { |s, _| !include_hidden && hidden_settings.include?(s) }
       .map do |s, v|
       value = send(s)
       opts = {
         setting: s,
         description: description(s),
-        default: defaults[s].to_s,
+        default: defaults.get(s, default_locale).to_s,
         value: value.to_s,
         category: categories[s],
         preview: previews[s],
@@ -162,7 +224,7 @@ module SiteSettingExtension
       }.merge(type_supervisor.type_hash(s))
 
       opts
-    end.unshift(defaults.locale_setting_hash)
+    end.unshift(locale_setting_hash)
   end
 
   def description(setting)
@@ -185,7 +247,7 @@ module SiteSettingExtension
         [s.name.to_sym, type_supervisor.to_rb_value(s.name, s.value, s.data_type)]
       }.to_a.flatten)]
 
-      defaults_view = defaults.all
+      defaults_view = defaults.all(new_hash[:default_locale])
 
       # add locale default and defaults based on default_locale, cause they are cached
       new_hash = defaults_view.merge!(new_hash)
@@ -242,7 +304,7 @@ module SiteSettingExtension
 
   def remove_override!(name)
     provider.destroy(name)
-    current[name] = defaults[name]
+    current[name] = defaults.get(name, default_locale)
     clear_cache!
   end
 
diff --git a/lib/site_settings/defaults_provider.rb b/lib/site_settings/defaults_provider.rb
index 7b1467a6535..6340ff91b9f 100644
--- a/lib/site_settings/defaults_provider.rb
+++ b/lib/site_settings/defaults_provider.rb
@@ -1,31 +1,23 @@
+# frozen_string_literal: true
+
 module SiteSettings; end
 
 # A cache for providing default value based on site locale
 class SiteSettings::DefaultsProvider
-  include Enumerable
-
-  CONSUMED_OPTS = %i[default locale_default].freeze
-  DEFAULT_LOCALE_KEY = :default_locale
-  DEFAULT_LOCALE = 'en'.freeze
-  DEFAULT_CATEGORY = 'required'.freeze
-
-  @@site_locales ||= DistributedCache.new('site_locales')
+  DEFAULT_LOCALE = 'en'
 
   def initialize(site_setting)
     @site_setting = site_setting
-    @site_setting.refresh_settings << DEFAULT_LOCALE_KEY
     @defaults = {}
     @defaults[DEFAULT_LOCALE.to_sym] = {}
-
-    refresh_site_locale!
   end
 
-  def load_setting(name_arg, value, opts = {})
+  def load_setting(name_arg, value, locale_defaults)
     name = name_arg.to_sym
     @defaults[DEFAULT_LOCALE.to_sym][name] = value
 
-    if (locale_default = opts[:locale_default])
-      locale_default.each do |locale, v|
+    if (locale_defaults)
+      locale_defaults.each do |locale, v|
         locale = locale.to_sym
         @defaults[locale] ||= {}
         @defaults[locale][name] = v
@@ -34,15 +26,19 @@ class SiteSettings::DefaultsProvider
   end
 
   def db_all
-    @site_setting.provider.all.delete_if { |s| s.name.to_sym == DEFAULT_LOCALE_KEY }
+    @site_setting.provider.all
   end
 
-  def all
-    @defaults[DEFAULT_LOCALE.to_sym].merge(@defaults[self.site_locale.to_sym] || {})
+  def all(locale = nil)
+    if locale
+      @defaults[DEFAULT_LOCALE.to_sym].merge(@defaults[locale.to_sym] || {})
+    else
+      @defaults[DEFAULT_LOCALE.to_sym].dup
+    end
   end
 
-  def get(name)
-    @defaults.dig(self.site_locale.to_sym, name.to_sym) ||
+  def get(name, locale = DEFAULT_LOCALE)
+    @defaults.dig(locale.to_sym, name.to_sym) ||
       @defaults.dig(DEFAULT_LOCALE.to_sym, name.to_sym)
   end
   alias [] get
@@ -50,81 +46,25 @@ class SiteSettings::DefaultsProvider
   # Used to override site settings in dev/test env
   def set_regardless_of_locale(name, value)
     name = name.to_sym
-    if @site_setting.has_setting?(name)
+    if name == :default_locale || @site_setting.has_setting?(name)
       @defaults.each { |_, hash| hash.delete(name) }
       @defaults[DEFAULT_LOCALE.to_sym][name] = value
       value, type = @site_setting.type_supervisor.to_db_value(name, value)
-      @defaults[self.site_locale.to_sym] ||= {}
-      @defaults[self.site_locale.to_sym][name] = @site_setting.type_supervisor.to_rb_value(name, value, type)
+      @defaults[SiteSetting.default_locale.to_sym] ||= {}
+      @defaults[SiteSetting.default_locale.to_sym][name] = @site_setting.type_supervisor.to_rb_value(name, value, type)
     else
       raise ArgumentError.new("No setting named '#{name}' exists")
     end
   end
 
-  def site_locale
-    @@site_locales[current_db]
-  end
-
-  def site_locale=(val)
-    val = val.to_s
-    raise Discourse::InvalidParameters.new(:value) unless LocaleSiteSetting.valid_value?(val)
-
-    if val != @@site_locales[current_db]
-      @site_setting.provider.save(DEFAULT_LOCALE_KEY, val, SiteSetting.types[:string])
-      refresh_site_locale!
-      @site_setting.refresh!
-      Discourse.request_refresh!
-    end
-
-    @@site_locales[current_db]
-  end
-
-  def each(&block)
-    self.all.each do |key, value|
-      block.call(key.to_sym, value)
-    end
-  end
-
-  def locale_setting_hash
-    {
-      setting: DEFAULT_LOCALE_KEY,
-      default: DEFAULT_LOCALE,
-      category: DEFAULT_CATEGORY,
-      description: @site_setting.description(DEFAULT_LOCALE_KEY),
-      type: SiteSetting.types[SiteSetting.types[:enum]],
-      preview: nil,
-      value: @@site_locales[current_db],
-      valid_values: LocaleSiteSetting.values,
-      translate_names: LocaleSiteSetting.translate_names?
-    }
-  end
-
-  def refresh_site_locale!
-    RailsMultisite::ConnectionManagement.each_connection do |db|
-      @@site_locales[db] =
-        if GlobalSetting.respond_to?(DEFAULT_LOCALE_KEY) &&
-            (global_val = GlobalSetting.send(DEFAULT_LOCALE_KEY)) &&
-            !global_val.blank?
-          global_val
-        elsif (db_val = @site_setting.provider.find(DEFAULT_LOCALE_KEY))
-          db_val.value.to_s
-        else
-          DEFAULT_LOCALE
-        end
-
-      @@site_locales[db]
-    end
-  end
-
   def has_setting?(name)
-    has_key?(name.to_sym) || has_key?("#{name.to_s}?".to_sym)
+    has_key?(name.to_sym) || has_key?("#{name.to_s}?".to_sym) || name.to_sym == :default_locale
   end
 
   private
 
   def has_key?(name)
-    @defaults[self.site_locale.to_sym]&.key?(name) ||
-      @defaults[DEFAULT_LOCALE.to_sym].key?(name) || name == DEFAULT_LOCALE_KEY
+    @defaults[DEFAULT_LOCALE.to_sym].key?(name)
   end
 
   def current_db
diff --git a/spec/components/site_setting_extension_spec.rb b/spec/components/site_setting_extension_spec.rb
index 1c8491c0099..f246a5588b9 100644
--- a/spec/components/site_setting_extension_spec.rb
+++ b/spec/components/site_setting_extension_spec.rb
@@ -505,6 +505,15 @@ describe SiteSettingExtension do
   end
 
   describe "shadowed_by_global" do
+
+    context "default_locale" do
+      it "supports adding a default locale via a global" do
+        global_setting :default_locale, 'zh_CN'
+        settings.default_locale = 'en'
+        expect(settings.default_locale).to eq('zh_CN')
+      end
+    end
+
     context "without global setting" do
       before do
         settings.setting(:trout_api_key, 'evil', shadowed_by_global: true)
diff --git a/spec/components/site_settings/defaults_provider_spec.rb b/spec/components/site_settings/defaults_provider_spec.rb
index e19b369f2bd..e4ca9a91091 100644
--- a/spec/components/site_settings/defaults_provider_spec.rb
+++ b/spec/components/site_settings/defaults_provider_spec.rb
@@ -26,20 +26,7 @@ describe SiteSettings::DefaultsProvider do
     new_settings(provider_local)
   end
 
-  describe 'inserts default_locale into refresh' do
-    it 'when initialize' do
-      expect(settings.refresh_settings.include?(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)).to be_truthy
-    end
-  end
-
   describe '.db_all' do
-    it 'collects values from db except default locale' do
-      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
-                             'en',
-                             SiteSetting.types[:string])
-      expect(settings.defaults.db_all).to eq([])
-    end
-
     it 'can collect values from db' do
       settings.provider.save('try_a', 1, SiteSetting.types[:integer])
       settings.provider.save('try_b', 2, SiteSetting.types[:integer])
@@ -55,11 +42,9 @@ describe SiteSettings::DefaultsProvider do
     end
 
     describe '.all' do
-      it 'returns all values according to the current locale' do
+      it 'returns all values according to locale' do
         expect(settings.defaults.all).to eq(test_override: 'default', test_default: 'test')
-        settings.defaults.site_locale = 'zh_CN'
-        settings.defaults.refresh_site_locale!
-        expect(settings.defaults.all).to eq(test_override: 'cn', test_default: 'test')
+        expect(settings.defaults.all('zh_CN')).to eq(test_override: 'cn', test_default: 'test')
       end
     end
 
@@ -72,11 +57,6 @@ describe SiteSettings::DefaultsProvider do
         expect(settings.defaults.get('test_override')).to eq 'default'
       end
 
-      it 'returns the default value according to current locale' do
-        expect(settings.defaults.get(:test_override)).to eq 'default'
-        settings.defaults.site_locale = 'zh_CN'
-        expect(settings.defaults.get(:test_override)).to eq 'cn'
-      end
     end
 
     describe '.set_regardless_of_locale' do
@@ -85,8 +65,7 @@ describe SiteSettings::DefaultsProvider do
       it 'sets the default value to a site setting regardless the locale' do
         settings.defaults.set_regardless_of_locale(:test_override, val)
         expect(settings.defaults.get(:test_override)).to eq val
-        settings.defaults.site_locale = 'zh_CN'
-        expect(settings.defaults.get(:test_override)).to eq val
+        expect(settings.defaults.get(:test_override, 'zh_CN')).to eq val
       end
 
       it 'handles the string' do
@@ -111,143 +90,13 @@ describe SiteSettings::DefaultsProvider do
         }.to raise_error(Discourse::InvalidParameters)
       end
     end
-
-    describe '.each' do
-      it 'yields the pair of site settings' do
-        expect { |b| settings.defaults.each(&b) }.to yield_successive_args([:test_override, 'default'], [:test_default, 'test'])
-        settings.defaults.site_locale = 'zh_CN'
-        expect { |b| settings.defaults.each(&b) }.to yield_successive_args([:test_override, 'cn'], [:test_default, 'test'])
-      end
-    end
-  end
-
-  describe '.site_locale' do
-    it 'returns the current site locale' do
-      expect(settings.defaults.site_locale).to eq 'en'
-    end
-
-    context 'when locale is set in the db' do
-      let(:db_val) { 'zr' }
-      let(:global_val) { 'gr' }
-
-      before do
-        settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
-                               db_val,
-                               SiteSetting.types[:string])
-        settings.defaults.refresh_site_locale!
-      end
-
-      it 'should load from database' do
-        expect(settings.defaults.site_locale).to eq db_val
-      end
-
-      it 'prioritizes GlobalSetting than value from db' do
-        GlobalSetting.stubs(:default_locale).returns(global_val)
-        settings.defaults.refresh_site_locale!
-        expect(settings.defaults.site_locale).to eq global_val
-      end
-
-      it 'ignores blank GlobalSetting' do
-        GlobalSetting.stubs(:default_locale).returns('')
-        settings.defaults.refresh_site_locale!
-        expect(settings.defaults.site_locale).to eq db_val
-      end
-    end
-
-  end
-
-  describe '.site_locale=' do
-    it 'should store site locale in a distributed cache' do
-      expect(settings.defaults.class.class_variable_get(:@@site_locales))
-        .to be_a(DistributedCache)
-    end
-
-    it 'changes and store the current site locale' do
-      settings.defaults.site_locale = 'zh_CN'
-
-      expect(settings.defaults.site_locale).to eq('zh_CN')
-    end
-
-    it 'changes and store the current site locale' do
-      expect { settings.defaults.site_locale = 'random' }.to raise_error(Discourse::InvalidParameters)
-      expect(settings.defaults.site_locale).to eq 'en'
-    end
-
-    it "don't change when it's shadowed" do
-      GlobalSetting.stubs(:default_locale).returns('shadowed')
-      settings.defaults.site_locale = 'zh_CN'
-      expect(settings.defaults.site_locale).to eq 'shadowed'
-    end
-
-    it 'refresh_site_locale! when called' do
-      settings.defaults.expects(:refresh_site_locale!)
-      settings.defaults.site_locale = 'zh_CN'
-    end
-
-    it 'refreshes the client when changed' do
-      Discourse.expects(:request_refresh!).once
-      settings.defaults.site_locale = 'zh_CN'
-    end
-
-    it "doesn't refresh the client when changed" do
-      Discourse.expects(:request_refresh!).never
-      settings.defaults.site_locale = 'en'
-    end
-  end
-
-  describe '.locale_setting_hash' do
-    it 'returns the hash for client display' do
-      result = settings.defaults.locale_setting_hash
-
-      expect(result[:setting]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)
-      expect(result[:default]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE)
-      expect(result[:type]).to eq(SiteSetting.types[SiteSetting.types[:enum]])
-      expect(result[:preview]).to be_nil
-      expect(result[:value]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE)
-      expect(result[:category]).to eq(SiteSettings::DefaultsProvider::DEFAULT_CATEGORY)
-      expect(result[:valid_values]).to eq(LocaleSiteSetting.values)
-      expect(result[:translate_names]).to eq(LocaleSiteSetting.translate_names?)
-      expect(result[:description]).not_to be_nil
-    end
   end
 
   describe '.load_setting' do
-    it 'adds a setting to the cache' do
-      settings.defaults.load_setting('new_a', 1)
+    it 'adds a setting to the cache correctly' do
+      settings.defaults.load_setting('new_a', 1, zh_CN: 7)
       expect(settings.defaults[:new_a]).to eq 1
-    end
-
-    it 'takes care of locale default' do
-      settings.defaults.load_setting(:new_b, 1, locale_default: { zh_CN: 2, zh_TW: 2 })
-      expect(settings.defaults[:new_b]).to eq 1
-    end
-  end
-
-  describe '.refresh_site_locale!' do
-    it 'loads the change to locale' do
-      expect(settings.defaults.site_locale).to eq 'en'
-      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
-                             'zh_CN',
-                             SiteSetting.types[:string])
-      settings.defaults.refresh_site_locale!
-      expect(settings.defaults.site_locale).to eq 'zh_CN'
-    end
-
-    it 'loads from GlobalSettings' do
-      expect(settings.defaults.site_locale).to eq 'en'
-      GlobalSetting.stubs(:default_locale).returns('fr')
-      settings.defaults.refresh_site_locale!
-      expect(settings.defaults.site_locale).to eq 'fr'
-    end
-
-    it 'prioritized GlobalSettings than db' do
-      expect(settings.defaults.site_locale).to eq 'en'
-      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
-                             'zh_CN',
-                             SiteSetting.types[:string])
-      GlobalSetting.stubs(:default_locale).returns('fr')
-      settings.defaults.refresh_site_locale!
-      expect(settings.defaults.site_locale).to eq 'fr'
+      expect(settings.defaults.get(:new_a, 'zh_CN')).to eq 7
     end
   end
 
@@ -266,7 +115,7 @@ describe SiteSettings::DefaultsProvider do
     end
 
     it 'default_locale always exists' do
-      expect(settings.defaults.has_setting?(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)).to be_truthy
+      expect(settings.defaults.has_setting?(:default_locale)).to be_truthy
     end
 
     it 'returns false when the key is not exist' do
diff --git a/spec/controllers/admin/site_settings_controller_spec.rb b/spec/controllers/admin/site_settings_controller_spec.rb
index b1f6007e932..c65247044c8 100644
--- a/spec/controllers/admin/site_settings_controller_spec.rb
+++ b/spec/controllers/admin/site_settings_controller_spec.rb
@@ -12,14 +12,18 @@ describe Admin::SiteSettingsController do
     end
 
     context 'index' do
-      it 'returns success' do
+      it 'returns valid info' do
         get :index, format: :json
-        expect(response).to be_successful
-      end
+        json = ::JSON.parse(response.body)
+        expect(json).to be_present
+        expect(response.status).to eq(200)
+        expect(json["site_settings"].length).to be > 100
 
-      it 'returns JSON' do
-        get :index, format: :json
-        expect(::JSON.parse(response.body)).to be_present
+        locale = json["site_settings"].select do |s|
+          s["setting"] == "default_locale"
+        end
+
+        expect(locale.length).to eq(1)
       end
     end
 
diff --git a/spec/multisite/jobs_spec.rb b/spec/multisite/jobs_spec.rb
index 076f6cea54a..2434bda3d49 100644
--- a/spec/multisite/jobs_spec.rb
+++ b/spec/multisite/jobs_spec.rb
@@ -5,7 +5,6 @@ RSpec.describe "Running Sidekiq Jobs in Multisite" do
 
   before do
     conn.config_filename = "spec/fixtures/multisite/two_dbs.yml"
-    SiteSetting.defaults.refresh_site_locale!
   end
 
   after do
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index fd977925cd5..e222e65e23e 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -153,7 +153,6 @@ RSpec.configure do |config|
     SiteSetting.provider.all.each do |setting|
       SiteSetting.remove_override!(setting.name)
     end
-    SiteSetting.defaults.site_locale = SiteSettings::DefaultsProvider::DEFAULT_LOCALE
 
     # very expensive IO operations
     SiteSetting.automatically_download_gravatars = false