The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Karl Marx (3 members)
- Khmer Rouge Atrocities (1 member)
- LGBT+ (5 members)
- LGBT+ people (3 members)
- LGBT+ topics (essays) (1 member)
- 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)
- Lemmygrad Community (1 member)
- Leninism (9 members)
- Letters between Marx and Engels (1 member)
- Liberalism (2 members)
- Liberals (8 members)
- Libertarianism (4 members)
- Library (31 members)
- Library documents from Albania (2 members)
- Library documents from Brazil (1 member)
- Library documents from China (22 members)
- Library documents from India (0 members)
- Library documents from Laos (2 members)
- Library documents from Mongolia (1 member)
- Library documents from Palestine (1 member)
- Library documents from Russia (1 member)
- Library documents from Vietnam (3 members)
- Library documents from the Brazilian Communist Party (4 members)
- Library documents from the CPUSA (2 members)
- Library documents from the DPRK (6 members)
- Library documents from the DRPK (0 members)
- Library documents from the Soviet Union (6 members)
- Library documents from the United States of America (8 members)