A monitor is a class of relatively small warship that is lightly armoured, often provided with disproportionately large guns, and originally designed for coastal warfare.
Allied monitors saw service in the Mediterranean in support of the British Eighth Army's desert and Italian campaigns.
The German, Yugoslav, Croatian, Romanian, Hungarian and Czech armed forces operated river monitors that saw combat during World War II.
The list includes armed vessels that served during the war and in the immediate aftermath, inclusive of localized ongoing combat operations, garrison surrenders, post-surrender occupation, colony re-occupation, troop and prisoner repatriation, to the end of 1945.
Ships are designated to the country under which they operated for the longest period of the Second World War, regardless of where they were built or previous service history.