# List of ships of World War II (O)

The List of ships of the Second World War contains major military vessels of the war, arranged alphabetically and by type. 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. For smaller vessels, see also list of World War II ships of less than 1000 tons. Some uncompleted Axis ships are included, out of historic interest. 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. Submarines show submerged displacement.
Click on headers to sort column alphabetically.
List of ships of World War II (O) :
| Ship | Country or organization | Class | Type | Displacement (tons) | First commissioned | Fate |
| O'Brien | United States Navy | Sims | destroyer | 1,570 | 2 March 1940 | sunk 19 October 1942 |
| Oakland | United States Navy | Atlanta | light cruiser | 6,000 | 17 July 1943 | decommissioned 1949, scrapped 1959 |
| Oakley | Royal Navy | Hunt | destroyer | 1,050 | 7 May 1942 | |
| Oakville | Royal Canadian Navy | Flower | corvette | 925 | 18 November 1941 | paid off 20 July 1945 |
| Obdurate | Royal Navy | O | minelayer destroyer | 1,540 | 3 September 1942 | paid off 1948, scrapped 1965 |
| Obedient | Royal Navy | O | minelayer destroyer | 1,540 | 30 October 1942 | paid off 1957, scrapped 1962 |
| Oberon | Royal Navy | Odin | submarine | 1,922 | 24 August 1927 | paid off 5 July 1944 |
| Ocean | Royal Navy | Colossus | aircraft carrier | 13,200 | 8 August 1945 | scrapped May 1962 |
| Odin | Royal Navy | Odin | submarine | 2,038 | 21 December 1929 | Sunk 14 June 1940 |
| Offa | Royal Navy | O | destroyer | 1,540 | 20 September 1941 | scrapped 1959 |
| Ōi | Imperial Japanese Navy | Kuma | light cruiser | 5,100 | 10 October 1921 | sunk by USS Flasher 19 July 1944 |
| Okinoshima | Imperial Japanese Navy | | minelayer | 4,290 | 30 September 1936 | sunk 12 May 1942 |
| Oklahoma | United States Navy | Nevada | battleship | 29,000 | 2 May 1916 | sunk 7 December 1941; raised and sunk under tow 1947 |
| Oklahoma City | United States Navy | Cleveland | light cruiser | 11,800 | 22 December 1944 | converted to missile cruiser 1960, sunk as target 1999 |
| Oktyabrskaya Revolutsiya | Soviet Navy | Gangut | battleship | 23,000 | 3 June 1909 | scrapped 1959 |
| Oldenburg | Kriegsmarine | | minelayer | 1,141 | 13 September 1943 | former water tanker Garigiliano captured from Italy |
| Olympus | Royal Navy | Odin | submarine | 2,038 | 14 June 1930 | sunk 8 May 1942 |
| Omaha | United States Navy | Omaha | light cruiser | 7,050 | 24 February 1923 | Scrapped February 1946 |
| Ommaney Bay | United States Navy | Casablanca | escort carrier | 7,800 | 11 February 1944 | scuttled 4 January 1945 |
| Onslaught | Royal Navy | O | destroyer | 1,540 | 19 June 1942 | scrapped 1977 |
| Onslow | Royal Navy | O | destroyer | 1,540 | 8 October 1941 | paid off April 1947 |
| Ontario | Royal Canadian Navy | Minotaur | light cruiser | 8,800 | July 1944 | laid up 15 October 1958 |
| Opportune | Royal Navy | O | minelayer destroyer | 1,540 | 14 August 1942 | paid off 1954, scrapped 1955 |
| Orchis | Royal Navy | Flower | corvette | 925 | 29 November 1940 | 21 August 1944 |
| Ordronaux | United States Navy | Benson | destroyer | 1,620 | 13 February 1943 | decommissioned 1947, scrapped 1973 |
| Orillia | Royal Canadian Navy | Flower | corvette | 925 | 25 November 1940 | paid off 2 July 1945 |
| Orella | Chile | Serrano | destroyer | 1,090 | | |
| Oribi | Royal Navy | O | destroyer | 1,540 | 5 July 1941 | paid off 1 January 1946 |
| Orion | Royal Navy | Leander | light cruiser | 7,000 | 18 January 1934 | scrapped 1949 |
| Orion | Kriegsmarine | | auxiliary cruiser | 15,700 | 9 December 1939 | sunk 4 May 1945 |
| Orkney | Royal Canadian Navy | River | frigate | 1,445 | 18 April 1944 | paid off 22 January 1946 |
| Orpheus | Royal Navy | Odin | submarine | 2,038 | 23 September 1930 | Sunk 19 June 1940 |
| Orwell | Royal Navy | O | minelayer destroyer | 1,540 | 17 October 1942 | |
| Orzeł | Poland | Orzeł | submarine | 1,100 | 2 February 1939 | sunk 11 June 1940 |
| Oscar II | Swedish Navy | Oscar II | coastal defence ship | | | paid off 1950, scrapped 1974 |
| Osiris | Royal Navy | Odin | submarine | 2,038 | 25 January 1929 | paid off 7 March 1945 |
| Oswald | Royal Navy | Odin | submarine | 2,038 | 1 May 1929 | Sunk 1 August 1940 |
| Ottawa | Royal Canadian Navy | C | destroyer | 1,375 | 15 June 1938 | sunk 14 September 1942 by U-91 |
| Otus | Royal Navy | Odin | submarine | 2,038 | 5 July 1929 | paid off March 1946 |
| Otway | Royal Navy | Odin | submarine | 1,922 | 15 June 1927 | paid off 1945 |
| Ouragan | French Navy Free French Naval Forces Poland | Bourrasque | destroyer | 1,319 | 19 January 1927 | to Poland 17 July 1940, to Free French 30 April 1941, scrapped 7 April 1949 |
| Outremont | Royal Canadian Navy | River | frigate | 1,445 | 27 November 1943 | paid off 7 June 1965 |
| Owen Sound | Royal Canadian Navy | Flower modified | corvette | 1,015 | 17 November 1943 | 19 July 1945 |
| Oxley | Royal Navy | Odin | submarine | 1,922 | 1 April 1927 | sunk by friendly fire 10 September 1939 |
| Oxlip | Royal Navy | Flower | corvette | 925 | 28 December 1941 | |
| Ōyodo | Imperial Japanese Navy | Ōyodo | light cruiser | 11,433 | 28 February 1943 | sunk 25 July 1945 |