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.

The Second Geneva Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea is one of the four treaties of the Geneva Conventions. The Geneva Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea was first adopted in 1949, replacing the Hague Convention (X) of 1907. It adapts the main protective regime of the First Geneva Convention to combat at sea.