diff --git a/INSTALLATION.md b/INSTALLATION.md
index b47d24cf..780328d8 100644
--- a/INSTALLATION.md
+++ b/INSTALLATION.md
@@ -1590,6 +1590,7 @@ define( 'CONSTANT_NAME', value );
 | FICTIONEER_QUERY_RESULT_CACHE_THRESHOLD | integer | Count of a query result required to be eligible for caching. Default `50`.
 | FICTIONEER_QUERY_RESULT_CACHE_LIMIT | integer | Number of query results cached if the feature is enabled. Default `50`.
 | FICTIONEER_QUERY_RESULT_CACHE_BREAK | integer | Limit the number of large query result cache uploads per request. Default `3`.
+| FICTIONEER_OAUTH_COOKIE_EXPIRATION | integer | Expiration time of the OAuth 2.0 login cookie in seconds. Default `259200` (3 days).
 | FICTIONEER_CACHE_PURGE_ASSIST | boolean | Whether to call the cache purge assist function on post updates. Default `true`.
 | FICTIONEER_RELATIONSHIP_PURGE_ASSIST | boolean | Whether to purge related post caches. Default `true`.
 | FICTIONEER_SHOW_SEARCH_IN_MENUS | boolean | Whether to show search page links in menus. Default `true`.
diff --git a/functions.php b/functions.php
index b70aa9b3..ff2dca0e 100644
--- a/functions.php
+++ b/functions.php
@@ -323,6 +323,11 @@ if ( ! defined( 'FICTIONEER_QUERY_RESULT_CACHE_BREAK' ) ) {
   define( 'FICTIONEER_QUERY_RESULT_CACHE_BREAK', 3 );
 }
 
+// Integer: OAuth login cookie lifetime
+if ( ! defined( 'FICTIONEER_OAUTH_COOKIE_EXPIRATION' ) ) {
+  define( 'FICTIONEER_OAUTH_COOKIE_EXPIRATION', 3 * DAY_IN_SECONDS );
+}
+
 /*
  * Booleans
  */
diff --git a/includes/functions/_module-oauth.php b/includes/functions/_module-oauth.php
index 99641de3..3f34910f 100644
--- a/includes/functions/_module-oauth.php
+++ b/includes/functions/_module-oauth.php
@@ -472,7 +472,7 @@ function fictioneer_oauth2_make_user( $user_data, $cookie ) {
 
       // Allow login to last three days
       add_filter( 'auth_cookie_expiration', function( $length ) {
-        return 3 * DAY_IN_SECONDS;
+        return FICTIONEER_OAUTH_COOKIE_EXPIRATION;
       });
 
       // Set authentication cookie