USS S-4 (SS-109) was an S-class submarine of the United States Navy. In 1927, she was sunk by being accidentally rammed by a United States Coast Guard destroyer with the loss of all hands but was raised and restored to service until stricken in 1936.

The United States' S-class submarines, often simply called S-boats, were the first class of submarines with a significant number built to United States Navy designs. They made up the bulk of the USN submarine service in the interwar years and could be found in every theater of operations. While not considered fleet submarines, they were the first submarines in the USN designed for open ocean, blue water operations. All previous submarines had been intended for harbor or coastal defense. These boats were intended to have greater speed and range than previous classes, with improved habitability and greater armament.