HMS Endymion was a 21-gun Ister-class wooden screw frigate, the third of four ships of this name to serve in the Royal Navy. She was the last wooden frigate built at Deptford Dockyard. She was commissioned in 1866 and spent much of her service based at Malta. In 1869–70 she sailed around the world as part of a Flying Squadron. She remained in front-line service until 1874.

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.