The Mercy class of hospital ships are converted San Clemente-class supertankers used by the United States Navy. Originally built in the 1970s by the National Steel and Shipbuilding Company, they were acquired by the Navy and converted into hospital ships, coming into service in 1986 and 1987.

A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital. Most are operated by the military forces of various countries, as they are intended to be used in or near war zones. In the 19th century, redundant warships were used as moored hospitals for seamen.