USS Pentheus (ARL-20) was one of 39 Achelous-class landing craft repair ships built for the United States Navy during World War II.

Originally laid down as LST–1115 by the Chicago Bridge and Iron Company of Seneca, Illinois on 29 September 1944; launched 22 December 1944; and placed in reduced commission 4 January 1945.

Proceeding to Baltimore, Maryland, she decommissioned 6 February 1945; underwent conversion; and was commissioned in full as USS Pentheus (ARL–20) 7 June 1945.

From Pearl Harbor, she steamed to Johnston Island for two weeks duty prior to getting underway for Green Cove Springs, Florida and inactivation.

Arriving 20 April she decommissioned and joined the Atlantic Reserve Fleet, where she remained until struck from the Naval Vessel Register 1 January 1960.