(covers information from several alternate timelines)
A hospital ship or medical ship was a starship whose primary function was to be used for medical purposes. This could include serving as a hospital, ambulance, or pharmacy. Because of this, they were typically not well armed with weapons or other defensive systems.
In the anti-time future, one such hospital ship was the USS Pasteur, operated by Starfleet Medical, as indicated by its emblems on the primary hull and their prominent presence on the bridge. In that same future, the Klingon Empire conquered the Romulan Star Empire and grew hostile towards the Federation. In 2395, there was a Terrellian plague outbreak on Romulus. Federation medical ships had permission from the Klingons for crossing the border, so they could deliver medical supplies to the planet. (TNG: "All Good Things...")
One subject discussed at a conference on Romulus during the Dominion War in 2375 was a proposal to transfer twenty-five Federation hospital ships to the Romulans. (DS9: "Inter Arma Enim Silent Leges")
|attack cruiser • attack fighter • battle cruiser • battleship • bird-of-prey • blockade runner • carrier • colony ship • combat cruiser • corvette • cruiser • destroyer • diplomatic vessel • dreadnought • escort vessel • explorer ship • flagship • freighter • frigate • garbage scow • heavy cruiser • holding vessel • hospital ship • interceptor • light cruiser • luxury liner • mining vessel • patrol ship • penal deportation vessel • pilot vessel • prison ship • raider • robot ship • runabout • science vessel • scout ship • star cruiser • starliner • starship • supply ship • support vessel • survey ship • tanker • timeship • trading vessel • training vessel • transport ship • tug • warbird • warship|