USS San Marcos (LSD-25) was a Casa Grande-class dock landing ship the United States Navy, named for the Castillo de San Marcos, the oldest masonry fort still standing in the United States. In 1911, the second-class battleship Texas had also briefly borne the name San Marcos, perhaps for the town of San Marcos, Texas. The ship served in the United States Navy from 1945 to 1970. In 1971, the vessel was loaned to the Spanish Navy as Galicia (TA31), before being outright transferred in 1974. In 1980, the vessel's pennant number was changed to L31. Galicia was taken out of service by the Spanish Navy in 1988 and was scrapped in 1989.

The Casa Grande class was a class of dock landing ships used by the Royal Navy and the United States Navy during the Second World War. Nineteen ships were planned, but two, USS Fort Snelling and USS Point Defiance were cancelled before being completed.