A museum ship, or sometimes memorial ship, is a ship that has been preserved and converted into a museum open to the public, for educational or memorial purposes. Some are also used for training and recruitment purposes, a use found mostly with the small number of museum ships that are still operational, i.e., capable of regular movement.

There are several hundred museum ships around the world, with around 175 of them organised in the Historic Naval Ships Association though there are also many non-naval museum ships as well, from general merchant ships to tugs and lightships. Many, if not most, museum ships are also associated with a maritime museum.

Despite the long history of sea travel, the ravages of the elements and the expense of maintenance has resulted in the destruction of nearly all the ships that were ever built, often by sinking, usually by being broken up and sold for scrap. Only a few have survived, sometimes because of historical significance, but more often simply due to luck and circumstance.