SS Mission San Carlos was a Type T2-SE-A2 tanker built for the United States Maritime Commission during World War II.

Mission San Carlos was laid down on 1 November 1943 under a Maritime Commission contract by Marinship Corporation, Sausalito, California: launched 12 February 1944; sponsored by Mrs. J. H. Pomeroy; and delivered 15 April 1944.

Chartered to Pacific Tankers, Inc. for operations on 15 April, she spent the remainder of the War providing allied forces overseas with the vital fuel needed to keep America's armies on the move (during which time she was awarded the National Defense Service Medal).

The ship was sold to Transwestern Associates on 16 May 1966 for conversion to a bulk carrier, but was instead resold that September to the Hudson Waterways Corporation and renamed Seatrain Maryland.

Upon completion of the conversion and delivery in April 1967 Seatrain Maryland, IMO 6709153, was chartered to the MSTS in support of overseas U.S. military operations, including the transport of material, equipment and aircraft to Vietnam.