A museum ship, also called a 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, mostly for the small number of museum ships that are still operational and thus capable of regular movement.^[1]

Several hundred museum ships are kept around the world, with around 175 of them organised in the Historic Naval Ships Association^[2] though many are not naval museum ships, from general merchant ships to tugs and lightships. Many, if not most, museum ships are also associated with a maritime museum.

Relatively few ships are preserved beyond their useful life, due to the high cost of maintaining them against the ravages of the elements. Most are broken up and sold for scrap, while a relative handful are sunk as naval target practice, scuttled to create artificial reefs, and so on. Some survive because of historical significance, but more often due to luck and circumstance. Since an old ship tied up at dockside, without attention, still decays and eventually sinks, the practice of recent years has been to form some sort of preservation society, solicit donations from governments or private individuals, organize volunteer labor from the enthusiasts, and open the restored ship to visitors, usually for a fee.

When the USN turns over one of their ships to a museum, a contract must be signed, stating that the Navy bears no responsibility for the costs of restoration, preservation and maintenance. Also, major pieces of equipment such as engines and generators must be permanently disabled. If the ship requires services such as electricity and water, they must come through shore connections.^[3]

The restoration and maintenance of museum ships presents problems for historians who are asked for advice, and the results periodically generate some controversy^{[citation needed]}. For instance, the rigging of sailing ships has almost never survived, and so the rigging plan must be reconstructed from various sources. Studying the ships also allows historians to analyze how life on and operation of the ships took place.^[4] Numerous scientific papers have been written on ship restoration and maintenance, and international conferences are held discussing the latest developments.^[5] Some years ago, the Barcelona Charter was signed by a variety of international owner organizations of traditional vessels, and provides certain accepted minimum criteria for the restoration and operation of traditional watercraft still in operation.^[6]

Another consideration is the distinction between a "real" museum ship, and a ship replica. As repairs accumulate over time, less and less of the ship is of the original materials, and the lack of old parts (or even "appropriate" work tools) may lead to the use of modern "short-cuts" (such as welding a metal plate instead of riveting it, as would be the case during the ships' historical period).^[7] Visitors without historical background are also often unable to distinguish between a historical museum ship and a (more-or-less historically relevant) ship replica, which may serve solely as a tourist attraction.^[4]

Typically the visitor enters via gangplank, wanders around on the deck, then goes below, usually using the original stairways, giving a sense of how the crew got around. The interior features restored but inactivated equipment, enhanced with mementos including old photographs, explanatory displays, pages from the ship's logs, menus, and the like. Some add recorded sound effects, audio tours or video displays to enhance the experience.

In some cases, the ships radio room has been brought back into use, with volunteers operating amateur radio equipment. Often, the callsign assigned is a variation on the original identification of the ship. For example, the submarine USS Cobia, which had the callsign NBQV, is now on the air as NB9QV. The World War II submarine USS Pampanito, berthed at the San Francisco Maritime National Historical Park, had the active service callsign NJVT and is now on the air as NJ6VT. In other cases, such as USS Missouri, a distinctive call (in this case KH6BB) is used. This radio work not only helps restore part of the vessel, but also provides worldwide publicity for the museum ship.

A number of the larger museum ships have begun to offer hosting for weddings, meetings, other events, and sleepovers, and on a few ships still seaworthy, cruises. In the United States, this includes USS Constitution's annual "turnaround", when the old ship is towed out into the harbor and brought back in facing the other way, so as to weather evenly. A place on the deck is by invitation or lottery only, and highly prized.^[8]

Many^[who?] consider the tourism appeal of an interesting old vessel on the city waterfront strong enough that any port city should showcase one or more museum ships. This may even include building a replica ship at great expense.^[9]

• HMS Victory: the only ship of the line that is preserved.
• Jylland: the only wooden screw frigate that is preserved.
• Georgios Averof: the only armored cruiser that is preserved
• USS Salem: the only heavy cruiser that is preserved.
• Mikasa: the only pre-dreadnought battleship that is preserved.
• USS Texas: the only dreadnought battleship that is preserved.
• The Polish destroyer ORP Błyskawica: currently preserved as a museum ship in Gdynia.
• German submarine U-995 of World War II used as a museum.
• USS Yorktown: the first aircraft carrier converted into a museum.
• USS Constellation: sloop-of-war, the last sail-only warship designed and built by the United States Navy, preserved as a museum ship in Baltimore.
• USS Olympia: one of two protected cruisers currently preserved.
• HMS Caroline: WW1 light cruiser.
• HMS Belfast: WW2 light cruiser.
• Huáscar: one of the earliest ironclad warships to be preserved afloat.
• HMY Britannia: former royal yacht of the British monarchy, now preserved in Edinburgh.
• USS Sarsfield: served in the Republic of China Navy as ROCS Te Yang (DDG-925), now preserved in Anping.
• Cutty Sark: 1869 clipper preserved at Greenwich, London
• Brunel's 1843 steamship SS Great Britain, preserved at Bristol
• USS Pueblo: captured by North Korea in 1968, preserved as a museum ship in Pyongyang.

• List of museum ships