HMHS is an acronym for His/Her Majesty's Hospital Ship.
The earliest record of British hospital ship was Goodwill, which briefly accompanied a Royal Navy squadron in the Mediterranean in 1608 or 1609. From 1665 the Royal Navy formally maintained two hospital ships at any time, these being either hired merchant ship or elderly sixth rates, modified from their original design by the removal of internal bulkheads and addition of ports cut through the deck and hull for ventilation. The limit of two hospital ships at a time remained in place until the Nine Years' War at century's end. In 1691 there were four hospital ships in service, rising to five in 1693 and six in 1696.
In addition to their sailing crew, these seventeenth century hospital ships were staffed by a surgeon and four surgeon's mates. Standard medical supplies were bandages, soap, needles and bedpans, and patients were issued with a clean pair of sheets. Infectious patients were 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 from patient's mouths.
Royal Fleet Auxiliary hospital ships: