diff --git chrome/browser/chrome_resource_bundle_helper.cc chrome/browser/chrome_resource_bundle_helper.cc
index 0cfc966050b60..bbc20cffaee1a 100644
--- chrome/browser/chrome_resource_bundle_helper.cc
+++ chrome/browser/chrome_resource_bundle_helper.cc
@@ -68,8 +68,10 @@ extern void InitializeLocalState(
 
 // Initializes the shared instance of ResourceBundle and returns the application
 // locale. An empty |actual_locale| value indicates failure.
-std::string InitResourceBundleAndDetermineLocale(PrefService* local_state,
-                                                 bool is_running_tests) {
+std::string InitResourceBundleAndDetermineLocale(
+    PrefService* local_state,
+    ui::ResourceBundle::Delegate* resource_bundle_delegate,
+    bool is_running_tests) {
 #if BUILDFLAG(IS_ANDROID)
   // In order for SetLoadSecondaryLocalePaks() to work ResourceBundle must
   // not have been created yet.
@@ -82,16 +84,8 @@ std::string InitResourceBundleAndDetermineLocale(PrefService* local_state,
            .empty());
 #endif
 
-  std::string preferred_locale;
-#if BUILDFLAG(IS_MAC)
-  // TODO(markusheintz): Read preference pref::kApplicationLocale in order
-  // to enforce the application locale.
-  // Tests always get en-US.
-  preferred_locale = is_running_tests ? "en-US" : std::string();
-#else
-  preferred_locale =
+  std::string preferred_locale =
       local_state->GetString(language::prefs::kApplicationLocale);
-#endif
 
 #if BUILDFLAG(IS_CHROMEOS_ASH)
   ui::ResourceBundle::SetLottieParsingFunctions(
@@ -103,7 +97,8 @@ std::string InitResourceBundleAndDetermineLocale(PrefService* local_state,
   // On a POSIX OS other than ChromeOS, the parameter that is passed to the
   // method InitSharedInstance is ignored.
   std::string actual_locale = ui::ResourceBundle::InitSharedInstanceWithLocale(
-      preferred_locale, nullptr, ui::ResourceBundle::LOAD_COMMON_RESOURCES);
+      preferred_locale, resource_bundle_delegate,
+      ui::ResourceBundle::LOAD_COMMON_RESOURCES);
   CHECK(!actual_locale.empty())
       << "Locale could not be found for " << preferred_locale;
 
@@ -155,6 +150,7 @@ std::string InitResourceBundleAndDetermineLocale(PrefService* local_state,
 
 std::string LoadLocalState(
     ChromeFeatureListCreator* chrome_feature_list_creator,
+    ui::ResourceBundle::Delegate* resource_bundle_delegate,
     bool is_running_tests) {
   base::FilePath user_data_dir;
   if (!base::PathService::Get(chrome::DIR_USER_DATA, &user_data_dir))
@@ -166,5 +162,6 @@ std::string LoadLocalState(
       new ChromeCommandLinePrefStore(base::CommandLine::ForCurrentProcess()));
 
   return InitResourceBundleAndDetermineLocale(
-      chrome_feature_list_creator->local_state(), is_running_tests);
+      chrome_feature_list_creator->local_state(), resource_bundle_delegate,
+      is_running_tests);
 }
diff --git chrome/browser/chrome_resource_bundle_helper.h chrome/browser/chrome_resource_bundle_helper.h
index 0b22e445bc3ff..1d7c6b319ba4b 100644
--- chrome/browser/chrome_resource_bundle_helper.h
+++ chrome/browser/chrome_resource_bundle_helper.h
@@ -7,12 +7,15 @@
 
 #include <string>
 
+#include "ui/base/resource/resource_bundle.h"
+
 class ChromeFeatureListCreator;
 
 // Loads the local state, and returns the application locale. An empty return
 // value indicates the ResouceBundle couldn't be loaded.
 std::string LoadLocalState(
     ChromeFeatureListCreator* chrome_feature_list_creator,
+    ui::ResourceBundle::Delegate* resource_bundle_delegate,
     bool is_running_tests);
 
 #endif  // CHROME_BROWSER_CHROME_RESOURCE_BUNDLE_HELPER_H_
diff --git components/language/core/browser/locale_util.cc components/language/core/browser/locale_util.cc
index aa43742055b04..e84f21ab963cc 100644
--- components/language/core/browser/locale_util.cc
+++ components/language/core/browser/locale_util.cc
@@ -17,11 +17,11 @@ std::string GetApplicationLocale(PrefService* local_state) {
   // LoadLocaleResources(), which is how the global locale is set.
   // TODO(asvitkine): We should try to refactor things so that the logic is not
   // duplicated in multiple files.
-#if !BUILDFLAG(IS_APPLE)
+
   // The pref isn't always registered in unit tests.
   if (local_state->HasPrefPath(prefs::kApplicationLocale))
     preferred_locale = local_state->GetString(prefs::kApplicationLocale);
-#endif
+
   // Note: The call below is necessary even if |preferred_locale| is empty, as
   // it will get the locale that should be used potentially from other sources,
   // depending on the platform (e.g. the OS locale on Mac).
diff --git ui/base/l10n/l10n_util.cc ui/base/l10n/l10n_util.cc
index 62b1b0bab1553..cc03d5c173ea6 100644
--- ui/base/l10n/l10n_util.cc
+++ ui/base/l10n/l10n_util.cc
@@ -502,25 +502,7 @@ bool CheckAndResolveLocale(const std::string& locale,
   return CheckAndResolveLocale(locale, resolved_locale, /*perform_io=*/true);
 }
 
-#if BUILDFLAG(IS_APPLE)
-std::string GetApplicationLocaleInternalMac(const std::string& pref_locale) {
-  // Use any override (Cocoa for the browser), otherwise use the preference
-  // passed to the function.
-  std::string app_locale = l10n_util::GetLocaleOverride();
-  if (app_locale.empty())
-    app_locale = pref_locale;
-
-  // The above should handle all of the cases Chrome normally hits, but for some
-  // unit tests, we need something to fall back too.
-  if (app_locale.empty())
-    app_locale = "en-US";
-
-  return app_locale;
-}
-#endif
-
-#if !BUILDFLAG(IS_APPLE)
-std::string GetApplicationLocaleInternalNonMac(const std::string& pref_locale) {
+std::string GetApplicationLocaleInternal(const std::string& pref_locale) {
   std::string resolved_locale;
   std::vector<std::string> candidates;
 
@@ -585,15 +567,6 @@ std::string GetApplicationLocaleInternalNonMac(const std::string& pref_locale) {
 
   return std::string();
 }
-#endif  // !BUILDFLAG(IS_APPLE)
-
-std::string GetApplicationLocaleInternal(const std::string& pref_locale) {
-#if BUILDFLAG(IS_APPLE)
-  return GetApplicationLocaleInternalMac(pref_locale);
-#else
-  return GetApplicationLocaleInternalNonMac(pref_locale);
-#endif
-}
 
 std::string GetApplicationLocale(const std::string& pref_locale,
                                  bool set_icu_locale) {