USS R-26 (SS-103) was an R-class coastal and harbor defense submarine of the United States Navy. Her keel was laid down 26 April 1917 by the Lake Torpedo Boat Company in Bridgeport, Connecticut; the R-boats built by Lake Torpedo Boat (R-21 through R-27) are sometimes considered a separate class from those built by Fore River Shipbuilding (R-1 through R-14) and Union Iron Works (R-15 through R-20). She was launched on 18 June 1919 sponsored by Mrs. J. Walter Barnett, and commissioned on 23 October 1919 with Lieutenant Joseph C. Arnold in command.