The USS S-4 (SS-109) was a United States Navy submarine, part of the S-class fleet. Launched on December 1, 1923, it was designed for coastal defense and reconnaissance missions. The submarine was 219 feet long and had a surface displacement of 1,000 tons. On December 17, 1927, the USS S-4 sank after a collision with the Coast Guard cutter USCGC Paulding. The incident occurred off the coast of Massachusetts, resulting in the loss of 40 crew members. The submarine was later salvaged in 1928, but the tragedy highlighted the dangers of submarine operations during that era.