USS Portunus (ARC-1) was an LSM-1-class landing ship medium acquired by the U.S. Navy for use during World War II as a landing craft for troops and, later, as a cable repair ship. Portunus was laid down by the Federal Shipbuilding and Drydock Co., Newark, New Jersey, as LSM–275 1 August 1944; launched 11 September 1944; and commissioned 6 October 1944.