The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Industrial Workers of the World (1 member)
- Industrial policies (1 member)
- Infoboxes without native name language parameter (8 members)
- Informational essays (2 members)
- Infrastructure projects (1 member)
- Instruments of the bourgeoisie (3 members)
- Insurgencies (1 member)
- Intelligence Operations (9 members)
- Intelligence agencies (2 members)
- Intelligence operations (1 member)
- Intergovernmental organizations (15 members)
- International Auxiliary Languages (0 members)
- International Communist Organisations (0 members)
- International auxiliary languages (2 members)
- International communist organizations (10 members)
- International socialist organizations (1 member)
- Interviews (10 members)
- Iran (2 members)
- Iran memes (1 member)
- Iranian state media (1 member)
- Irish Marxists (2 members)
- Irish organizations (1 member)
- Irish republicans (3 members)
- Irish socialists (2 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)
- KKE comrades (0 members)
- 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)