The USS O-1 was a submarine of the United States Navy, commissioned in 1918. It was part of the O-class submarines, designed for coastal defense and reconnaissance. The vessel was 165 feet long and had a surface displacement of around 500 tons. During its service, the USS O-1 operated primarily in the Atlantic Ocean and was involved in various training exercises. It was decommissioned in 1924 and later sold for scrap in 1931. The submarine played a role in the early development of underwater warfare tactics for the U.S. Navy.