diff --git a/config/configuration.yml.example b/config/configuration.yml.example
index bff4c9740..14acb16a7 100644
--- a/config/configuration.yml.example
+++ b/config/configuration.yml.example
@@ -209,6 +209,17 @@ default:
   # allowed values: :memory, :file, :memcache
   #openid_authentication_store: :memory
 
+  # URL of the avatar service
+  #
+  # By default, Redmine uses Gravatar as the avatar service for displaying
+  # the user's icon. You can swich to another Gravatar-compatible service
+  # such as Libravatar.
+  #
+  # Examples:
+  # avatar_service_url: https://www.gravatar.com
+  # avatar_service_url: https://seccdn.libravatar.org
+  avatar_service_url:
+
 # specific configuration options for production environment
 # that overrides the default ones
 production:
diff --git a/lib/plugins/gravatar/lib/gravatar.rb b/lib/plugins/gravatar/lib/gravatar.rb
index 7c2fca6d3..1554672a9 100644
--- a/lib/plugins/gravatar/lib/gravatar.rb
+++ b/lib/plugins/gravatar/lib/gravatar.rb
@@ -39,6 +39,8 @@ module GravatarHelper
     :ssl => false,
   }
 
+  AVATAR_SERVICE_URL = Redmine::Configuration['avatar_service_url'] || 'https://www.gravatar.com'
+
   # The methods that will be made available to your views.
   module PublicMethods
 
@@ -63,7 +65,7 @@ module GravatarHelper
 
     # Returns the base Gravatar URL for the given email hash
     def gravatar_api_url(hash)
-      'https://www.gravatar.com/avatar/' + hash.to_s
+      +"#{AVATAR_SERVICE_URL}/avatar/#{hash}"
     end
 
     # Return the gravatar URL for the given email address.