The USS S-45 was a United States Navy submarine, part of the S-class fleet, designed for coastal defense during the early 20th century. Launched in 1924, it was built at the Fore River Shipyard in Quincy, Massachusetts. The submarine was primarily used for training and testing purposes, contributing to the development of submarine warfare tactics. Commissioned in 1925, the USS S-45 served in various capacities until it was decommissioned in 1931. After its service, the submarine was sold for scrap in 1934. The S-45 played a role in the evolution of submarine technology during a pivotal time in naval history.