Very much depends on the cruise ship, and it’s often based on their country of origin. Here are some examples:
in the help of P&O cruises (a British-American cruise line) :
Oceana and Britannia also have US 2 pin sockets in addition to UK 3 pin sockets
The standard electrical supply in the United Kingdom is 50HZ (cycles) and 240V.
The supply on board is:
Adonia -220V / 60HZ
Arcadia - 220V / 110V / 60HZ
Aurora - 220V / 60HZ
Azura - 230V / 115V / 60HZ
Oceana - 220V / 110V / 60HZ
Oriana - 220V / 60HZ
Ventura - 230V / 115V / 60HZ
and Iglu, a UK cruise agent, lists many cruise lines :
**Cunard**
British three-pin, 220v sockets and 110v two-pin sockets are available.
**Costa Cruises**
Continental Europe 220v two-pin sockets
**Cruise and Maritime**
Continental Europe two-pin, 220v/110v sockets
**Disney Cruise Line**
US two-pin 110v sockets
**Celebrity Cruises**
A 220v Continental Europe two-pin socket and multiple US 110v two-pin sockets.
**Fred. Olsen**
Both US 110v two-pin sockets and Continental Europe 220v two-pin sockets
**MSC Cruises**
Both US 110v two-pin sockets and Continental Europe 220v two-pin sockets
**Norwegian Cruise Line**
US 110v two-pin sockets.
**P&O Cruises**
British 220v three-pin sockets.
**Princess Cruises**
US 110v two-pin sockets
**Royal Caribbean**
US 110v two-pin sockets
**Carnival**
US 110v two-pin sockets
**Holland America Line**
Equipped with both standard 110v and 220v outlets
It will depend on the ship. Cunard seems to have one US + one UK plug officially, and if you search around you find some more (by unplugging TV etc.), but they have tons of British customers. Other cruise ships might have US + European.
Credit:stackoverflow.com‘