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- Kalanpää (Finland): 52-ton Ajonpää class minesweeper
- Kalev (Estonia): 834-ton submarine
- Karjala (Finland): 342-ton gunboat
- Khrabry (Bulgaria): 97-ton minesweeper
- Kiang Chen (China): 550-ton gunboat
- Kiang Heng (China): 550-ton gunboat
- Kiang Hsi (China): 140-ton gunboat
- Kiang Kun (China): 140-ton gunboat
- Kiang Li (China): 550-ton gunboat
- Kiang Yuan (China): 550-ton gunboat
- King (Argentina): 900-ton gunboat
- Kiwi (New Zealand): 607-ton Bird class minesweeper
- Kjell (Norway): 84-ton 2nd class torpedo boat
- King Haakon VII (Norway): 357-ton PC class escort ship
- Komendant Piłsudski (Poland) 342-ton Gunboat
- Kung Chen (China): 90-ton river gunboat
- Kvintus (Denmark): 186-ton minlayer, became Fürstenburg (Germany)
Read more about this topic: List Of World War II Ships Of Less Than 1000 Tons