diff --git a/CHANGELOG.md b/CHANGELOG.md
index 04328b760..0adbeb67a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,16 +6,18 @@
   * Remove `SecretKeyFinder` and use `app.secret_key_base` as the default secret key for `Devise.secret_key` if a custom `Devise.secret_key` is not provided.
 
     This is potentially a breaking change because Devise previously used the following order to find a secret key:
-    
+
     ```
     app.credentials.secret_key_base > app.secrets.secret_key_base > application.config.secret_key_base > application.secret_key_base
     ```
-    
+
     Now, it always uses `application.secret_key_base`. Make sure you're using the same secret key after the upgrade; otherwise, previously generated tokens for `recoverable`, `lockable`, and `confirmable` will be invalid.
     https://github.com/heartcombo/devise/pull/5645
 
 * enhancements
   * Removed deprecations warning output for `Devise::Models::Authenticatable::BLACKLIST_FOR_SERIALIZATION` (@soartec-lab)
+  * Add Rails 8 support.
+    - Routes are lazy-loaded by default in test and development environments now so Devise loads them before `Devise.mappings` call.
 
 Please check [4-stable](https://github.com/heartcombo/devise/blob/4-stable/CHANGELOG.md)
 for previous changes.
diff --git a/lib/devise.rb b/lib/devise.rb
index 3d9dc7886..5b7417ed6 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -274,8 +274,14 @@ module Test
   # PRIVATE CONFIGURATION
 
   # Store scopes mappings.
-  mattr_reader :mappings
   @@mappings = {}
+  def self.mappings
+    # Starting from Rails 8.0, routes are lazy-loaded by default in test and development environments.
+    # However, Devise's mappings are built during the routes loading phase.
+    # To ensure it works correctly, we need to load the routes first before accessing @@mappings.
+    Rails.application.try(:reload_routes_unless_loaded)
+    @@mappings
+  end
 
   # OmniAuth configurations.
   mattr_reader :omniauth_configs