The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Irish Marxists (5 members)
- Irish organizations (14 members)
- Irish republicans (10 members)
- Irish socialists (4 members)
- Irish trade unionists (2 members)
- Islam (7 members)
- Japan (5 members)
- Jihadism (3 members)
- Joseph Stalin (9 members)
- Journalism (3 members)
- Journalists (19 members)
- Journalists by country (3 members)
- Juche (2 members)
- Jucheists (11 members)
- Judaism (1 member)
- Julius Nyerere (2 members)
- Junkers (1 member)
- KKE comrades (0 members)
- Karl Marx (3 members)
- Khmer Rouge Atrocities (1 member)
- Korea (1 member)
- LGBT+ (5 members)
- LGBT+ people (3 members)
- LGBT+ topics (essays) (2 members)
- Labor (3 members)
- Labor movement (4 members)
- Labor movement by country (1 member)
- Labor movement in the United States (7 members)
- Labor organizers (3 members)
- Labor strikes (10 members)
- Labor strikes by country (1 member)
- Labor strikes by year (2 members)
- Labor strikes in 2021 (3 members)
- Labor strikes in 2022 (1 member)
- Labor strikes in the United States (5 members)
- Langston Hughes (1 member)
- Language (6 members)
- Laotian leaders (3 members)
- Latin American countries (15 members)
- Law enforcement (2 members)
- Leaders (9 members)
- Leaders by country (1 member)
- Leaders of political parties (1 member)
- Left-wing ideologies (28 members)
- Left communism (4 members)
- Left communists (2 members)
- Leftist music (5 members)
- Legislatures (1 member)
- Lemmygrad Community (1 member)
- Leninism (9 members)