The hospital ship occurs as ship designated for primary function as a medical treatment facility or hospital; most come operated per military forces or navies of various countries around the world.

An early lesson of the hospital ship was Red Rover in the 1860s, which aided the wounded soldiers of both sides during the American Civil War.

USNS Mercy and USNS Comfort are hospital ships operated by the United States Navy and the largest ambulances extant.

Modern hospital ships display big Red Crosses or Red Crescents to enjoy Geneva convention protection under the laws of war.