A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads, typically exceeding 1,500 t (1,500 long tons; 1,700 short tons) for modern ships. The largest crane vessels are used for offshore construction.

The cranes are fitted to conventional monohulls and barges, but the largest crane vessels are often catamaran or semi-submersible types which provide enhanced stability. Many crane vessels are fitted with one or more rotating cranes. Some of the largest crane vessels use fixed sheerlegs instead; in these designs, the crane is cannot rotate relative to the ship, and the vessel therefore is manoeuvered to place loads. Other vessels use large gantry cranes and straddle the load.