- Kowalski, Artur1
- Kracauer, Siegfried1
- Krakovský, Roman1
- Kravchenko, Victor1
- Kropotkin, Petr Alekseevich1
- Krystufek, Zdenek1
- Krüger, Horst1
- Kulski, Władysław Wszebór1
- Kupiecki, Robert1
- Kállai, Gyula1
- Kéhayan, Nina1
- Labin, Suzanne1
- Lafargue, Paul1
- Langer, Paul Fritz1
- Lavrova, L. F.1
- Leites, Nathan1
- Lenin, Vladimir Il'ich1
- Lenin, Vladimir Ilʹich1
- Lessing, Pieter1
- Levenson, Joseph Richmond1