I
| Class | Country | Type | Launch years | Displacement (tons) | Number |
| I | UK | destroyer | 1936-41 | 1,370 | 11 |
| Illustrious | UK | aircraft carrier | 23,000 | 6 | |
| Implacable | UK | aircraft carrier | 23,000 | 2 | |
| Independence | US | aircraft carrier | 11,000 | 9 | |
| Iowa | US | battleship | 1942-50 | 48,110 | 4 completed |
| Ise | Japan | battleship | 1916-17 | 31,762 | 2 |
| Isles | UK | naval trawler | 545 | 168 | |
| Izumo | Japan | armored cruiser | 1898 | 9,750 | 2 |
Read more about this topic: List Of World War II Ship Classes