A
| Class | Country | Type | Launch years | Displacement (tons) | Number |
| A | UK | destroyer | 1929-30 | 1,350 | 11 |
| A | Norway | submarine | approx. 1914 | 268 | 3 |
| Admiral | UK | battlecruiser | 1918 | 48,000 | 4 planned, 1 completed |
| Abdiel = Manxman | UK | minelayer | 1940-44 | 2,650 | 6 |
| Acre | Brazil | destroyer | 1943-46 | 1,340 | 6 |
| Admiral Hipper | Germany | heavy cruiser | 1937-39 | 14,000 | 5, 3 completed |
| Ægir = B | Denmark | submarine | 1915 | 237 | 5 |
| Aetos | Greece | destroyer | 1911 | 1,050 | 4 |
| Agano | Japan | light cruiser | 1941-44 | 6,650 | 4 |
| Ahven | Finland | minesweeper | approx. 1937 | 17 | 6 |
| Aigle = 2400 tonnes | France | destroyer | 1930-31 | 2,441 | 6 |
| Aikoku Maru | Japan | armed merchant cruiser | 17,000 | 3 | |
| Akagi Maru | Japan | armed merchant cruiser | 1941 | 17,000 | 1 |
| Akatsuki | Japan | destroyer | 1931-32 | 1,680 | 4 |
| Akitsushima | Japan | seaplane tender | 19 April 1942 | 4,900 | 1 |
| Akizuki | Japan | destroyer | 1941-44 | 2,700 | 12 completed |
| Alaska | US | large cruiser | 1943-50 | 29,779 | 2 completed |
| Algerien | France | destroyer | 1943-44 | 1,300 | 6 |
| Algerine | UK | minesweeper | 1942-44 | 850 | 109 |
| Allen M. Sumner | US | destroyer | 1943-44 | 2,200 | 58 |
| Amphion or "A" | UK | submarine | 1944–1945 | 1,620 (submerged) | 2 commissioned of 16 by end of war |
| Andrea Doria | Italy | battleship | 1913 | 23,800 | 2 |
| Andromeda | US | Attack Cargo Ship | 1943-45 | 6,761 tons | 34 |
| Aoba | Japan | heavy cruiser | 1926 | 10,822 | 2 |
| Arethusa | UK | light cruiser | 1934-36 | 5,250 | 4 |
| Asashio | Japan | destroyer | 1936-37 | 1,961 | 10 |
| Astoria = New Orleans | US | heavy cruiser | 1933-36 | 9,375 | 7 |
| Asama | Japan | cruiser | 1898 | 9,700 | 2 |
| Atlanta | US | light cruiser | 1941-46 | 6,000 | 11 |
| Attacker = US Bogue | UK | escort aircraft carrier | 16,000 | 11 | |
| Awata Maru | Japan | armed merchant cruiser | 7,398 | 1 |
Read more about this topic: List Of World War II Ship Classes