diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index c9bf901ae1576..196eca5afd341 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -4047,7 +4047,13 @@ public function get_queried_object() {
 				}
 			}
 
-			$this->queried_object = get_userdata( $this->queried_object_id );
+			if ( $this->queried_object_id ) {
+				$user = get_userdata( $this->queried_object_id );
+
+				if ( $user ) {
+					$this->queried_object = $user;
+				}
+			}
 		}
 
 		return $this->queried_object;
diff --git a/tests/phpunit/tests/query.php b/tests/phpunit/tests/query.php
index 40d23816d1ab6..3a91a48ab9921 100644
--- a/tests/phpunit/tests/query.php
+++ b/tests/phpunit/tests/query.php
@@ -723,6 +723,40 @@ public function test_get_queried_object_should_work_for_author_name_before_get_p
 		$this->assertSame( get_queried_object_id(), $user_id );
 	}
 
+	/**
+	 * @ticket 65400
+	 */
+	public function test_get_queried_object_should_return_null_when_author_id_is_non_existent() {
+		add_action(
+			'parse_query',
+			static function ( $query ) {
+				$query->is_author = true;
+				$query->set( 'author', 999999 );
+			}
+		);
+
+		$this->go_to( home_url( '/' ) );
+
+		$this->assertNull( get_queried_object() );
+	}
+
+	/**
+	 * @ticket 65400
+	 */
+	public function test_get_queried_object_should_return_null_when_author_is_unset() {
+		// Trigger is_author without a valid author query var.
+		add_action(
+			'parse_query',
+			static function ( $query ) {
+				$query->is_author = true;
+			}
+		);
+
+		$this->go_to( home_url( '/' ) );
+
+		$this->assertNull( get_queried_object() );
+	}
+
 	/**
 	 * Tests that the `posts_clauses` filter receives an array of clauses
 	 * with the other `posts_*` filters applied, e.g. `posts_join_paged`.