HMS Atlas was a 91-gun second rate ship which was never completed and spent her entire service in reserve or as a hospital ship. She was launched in 1860, and lent to the Metropolitan Asylums Board for use as a hospital ship in 1881, and sold to them in 1885. Atlas served until 1904, when she was sold for breaking.

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.