- Kautsky, Karl1
- Kelly, David1
- Kivinen, Markku1
- Koestler, Arthur1
- Kosinski, Jerzy1
- Kotkin, Stephen1
- Kravchenko, Victor1
- Kulski, Władysław Wszebór1
- Kéhayan, Nina1
- Leites, Nathan1
- Lenin, Vladimir Il'ich1
- Lenin, Vladimir Iliʹch1
- Lockhart, Robert Hamilton Bruce1
- Lowe, Donald M.1
- Luxemburg, Rosa1
- Malakhov, Anatolii Alekseevich1
- Malaurie, Guillaume1
- Medvedev, Roy Aleksandrovich1
- Mihajlov, Mihajlo1
- Miller, William J.1