diff --git a/app/helpers/languages_helper.rb b/app/helpers/languages_helper.rb
index 0d4edceb7b5..87f0f288d36 100644
--- a/app/helpers/languages_helper.rb
+++ b/app/helpers/languages_helper.rb
@@ -224,7 +224,7 @@ module LanguagesHelper
     'en-GB': 'English (British)',
     'es-AR': 'Español (Argentina)',
     'es-MX': 'Español (México)',
-    'fr-QC': 'Français (Canadien)',
+    'fr-CA': 'Français (Canadien)',
     'pt-BR': 'Português (Brasil)',
     'pt-PT': 'Português (Portugal)',
     'sr-Latn': 'Srpski (latinica)',
diff --git a/app/javascript/mastodon/locales/fr-QC.json b/app/javascript/mastodon/locales/fr-CA.json
similarity index 100%
rename from app/javascript/mastodon/locales/fr-QC.json
rename to app/javascript/mastodon/locales/fr-CA.json
diff --git a/config/initializers/i18n.rb b/config/initializers/i18n.rb
index 39b7a3cc40f..1c1cea1b945 100644
--- a/config/initializers/i18n.rb
+++ b/config/initializers/i18n.rb
@@ -31,7 +31,7 @@ Rails.application.configure do
     :fi,
     :fo,
     :fr,
-    :'fr-QC',
+    :'fr-CA',
     :fy,
     :ga,
     :gd,
diff --git a/config/locales/activerecord.fr-QC.yml b/config/locales/activerecord.fr-CA.yml
similarity index 99%
rename from config/locales/activerecord.fr-QC.yml
rename to config/locales/activerecord.fr-CA.yml
index 607758add64..1a83a0e9e26 100644
--- a/config/locales/activerecord.fr-QC.yml
+++ b/config/locales/activerecord.fr-CA.yml
@@ -1,5 +1,5 @@
 ---
-fr-QC:
+fr-CA:
   activerecord:
     attributes:
       poll:
diff --git a/config/locales/devise.fr-QC.yml b/config/locales/devise.fr-CA.yml
similarity index 99%
rename from config/locales/devise.fr-QC.yml
rename to config/locales/devise.fr-CA.yml
index 8c1a94dab66..4c693600242 100644
--- a/config/locales/devise.fr-QC.yml
+++ b/config/locales/devise.fr-CA.yml
@@ -1,5 +1,5 @@
 ---
-fr-QC:
+fr-CA:
   devise:
     confirmations:
       confirmed: Votre adresse de courriel a été validée avec succès.
diff --git a/config/locales/doorkeeper.fr-QC.yml b/config/locales/doorkeeper.fr-CA.yml
similarity index 99%
rename from config/locales/doorkeeper.fr-QC.yml
rename to config/locales/doorkeeper.fr-CA.yml
index 043b4a6cda9..9d671569f52 100644
--- a/config/locales/doorkeeper.fr-QC.yml
+++ b/config/locales/doorkeeper.fr-CA.yml
@@ -1,5 +1,5 @@
 ---
-fr-QC:
+fr-CA:
   activerecord:
     attributes:
       doorkeeper/application:
diff --git a/config/locales/fr-QC.yml b/config/locales/fr-CA.yml
similarity index 99%
rename from config/locales/fr-QC.yml
rename to config/locales/fr-CA.yml
index 3d85ced1514..c43fa013c74 100644
--- a/config/locales/fr-QC.yml
+++ b/config/locales/fr-CA.yml
@@ -1,5 +1,5 @@
 ---
-fr-QC:
+fr-CA:
   about:
     about_mastodon_html: 'Le réseau social de l''avenir : pas de publicité, pas de surveillance institutionnelle, conception éthique et décentralisation ! Gardez le contrôle de vos données avec Mastodon !'
     contact_missing: Non défini
diff --git a/config/locales/simple_form.fr-QC.yml b/config/locales/simple_form.fr-CA.yml
similarity index 99%
rename from config/locales/simple_form.fr-QC.yml
rename to config/locales/simple_form.fr-CA.yml
index 7a95a1c882a..f5a2a428e9c 100644
--- a/config/locales/simple_form.fr-QC.yml
+++ b/config/locales/simple_form.fr-CA.yml
@@ -1,5 +1,5 @@
 ---
-fr-QC:
+fr-CA:
   simple_form:
     hints:
       account:
diff --git a/db/migrate/20240109103012_fix_canadian_french_locale.rb b/db/migrate/20240109103012_fix_canadian_french_locale.rb
new file mode 100644
index 00000000000..1b8ef7a4afa
--- /dev/null
+++ b/db/migrate/20240109103012_fix_canadian_french_locale.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class FixCanadianFrenchLocale < ActiveRecord::Migration[7.0]
+  class User < ApplicationRecord
+    # Dummy class, to make migration possible across version changes
+  end
+
+  disable_ddl_transaction!
+
+  def up
+    User.where(locale: 'fr-QC').in_batches do |users|
+      users.update_all(locale: 'fr-CA')
+    end
+  end
+
+  def down
+    User.where(locale: 'fr-CA').in_batches do |users|
+      users.update_all(locale: 'fr-QC')
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 4ea9744f401..cbe54c1db79 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2023_12_22_100226) do
+ActiveRecord::Schema[7.1].define(version: 2024_01_09_103012) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
diff --git a/lib/tasks/tests.rake b/lib/tasks/tests.rake
index 209a73efa5e..c3a9dbfd738 100644
--- a/lib/tasks/tests.rake
+++ b/lib/tasks/tests.rake
@@ -83,6 +83,11 @@ namespace :tests do
         puts 'Default posting language not migrated as expected for kmr users'
         exit(1)
       end
+
+      unless Account.find_local('qcuser').user.locale == 'fr-CA'
+        puts 'Locale for fr-QC users not updated to fr-CA as expected'
+        exit(1)
+      end
     end
 
     desc 'Populate the database with test data for 2.4.3'
@@ -142,13 +147,19 @@ namespace :tests do
         INSERT INTO "accounts"
           (id, username, domain, private_key, public_key, created_at, updated_at)
         VALUES
-          (10, 'kmruser', NULL, #{user_private_key}, #{user_public_key}, now(), now());
+          (10, 'kmruser', NULL, #{user_private_key}, #{user_public_key}, now(), now()),
+          (11, 'qcuser', NULL, #{user_private_key}, #{user_public_key}, now(), now());
 
         INSERT INTO "users"
           (id, account_id, email, created_at, updated_at, admin, locale, chosen_languages)
         VALUES
           (4, 10, 'kmruser@localhost', now(), now(), false, 'ku', '{en,kmr,ku,ckb}');
 
+        INSERT INTO "users"
+          (id, account_id, email, created_at, updated_at, locale)
+        VALUES
+          (5, 11, 'qcuser@localhost', now(), now(), 'fr-QC');
+
         INSERT INTO "settings"
           (id, thing_type, thing_id, var, value, created_at, updated_at)
         VALUES