diff --git a/src/Illuminate/Database/Eloquent/Relations/Relation.php b/src/Illuminate/Database/Eloquent/Relations/Relation.php
index b5e8864f0937..cba4ca2afed0 100755
--- a/src/Illuminate/Database/Eloquent/Relations/Relation.php
+++ b/src/Illuminate/Database/Eloquent/Relations/Relation.php
@@ -501,6 +501,17 @@ public static function getMorphedModel($alias)
         return static::$morphMap[$alias] ?? null;
     }
 
+    /**
+     * Get the alias associated with a custom polymorphic class.
+     *
+     * @param  string  $className
+     * @return int|string|null
+     */
+    public static function getMorphAlias(string $className)
+    {
+        return array_flip(static::$morphMap)[$className] ?? null;
+    }
+
     /**
      * Handle dynamic method calls to the relationship.
      *
diff --git a/tests/Database/DatabaseEloquentRelationTest.php b/tests/Database/DatabaseEloquentRelationTest.php
index f1a8aab3fb11..47bd92710bcf 100755
--- a/tests/Database/DatabaseEloquentRelationTest.php
+++ b/tests/Database/DatabaseEloquentRelationTest.php
@@ -235,6 +235,14 @@ public function testSettingMorphMapWithNumericKeys()
         Relation::morphMap([], false);
     }
 
+    public function testGetMorphAlias()
+    {
+        Relation::morphMap(['user' => 'App\User']);
+
+        $this->assertEquals('user', Relation::getMorphAlias('App\User'));
+        $this->assertNull(Relation::getMorphAlias('Does\Not\Exist'));
+    }
+
     public function testWithoutRelations()
     {
         $original = new EloquentNoTouchingModelStub;