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 (mostly navies) of various countries, as they are intended to be used in or near war zones.
Although attacking a hospital ship is a war crime, belligerent navies have the right to board such ships for inspections.
In the nineteenth century redundant warships were used as moored hospitals for seamen.
Hospital ships possibly existed in ancient times. The Athenian Navy had a ship named Therapia, and the Roman Navy had a ship named Aesculapius, their names indicating that they may have been hospital ships.
The earliest British hospital ship may have been the vessel Goodwill, which accompanied a Royal Navy squadron in the Mediterranean in 1608 and was used to house the sick sent aboard from other ships. However this experiment in medical care was short-lived, with Goodwill assigned to other tasks within a year and her complement of convalescents simply left behind at the nearest port. It was not until the mid-seventeenth century that any Royal Navy vessels were formally designated as hospital ships, and then only two throughout the fleet. These were either hired merchant ship or elderly sixth rates, with the internal bulkheads removed to create more room, and additional ports cut through the deck and hull to increase internal ventilation.
In addition to their sailing crew, these seventeenth century hospital ships were staffed by a surgeon and four surgeon's mates. The standard issue of medical supplies were bandages, soap, needles and bedpans. Patients were offered a beds or rug to rest upon, and given a clean pair of sheets. These early hospital ships were for the care of the sick rather than the wounded, with patients quartered according to their symptoms and infectious cases quarantined from the general population behind a sheet of canvas. The quality of food was very poor. In the 1690s the surgeon aboard Siam complained that the meat was in an advanced state of putrefaction, the biscuits were weevil-ridden and bitter, and the bread was so hard that it stripped the skin off patient's mouths.