The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Tigh (TOS) (1 member)
- Tigh Me Up, Tigh Me Down (38 members)
- Torn (56 members)
- Toys (23 members)
- Tracking categories (1 member)
- Twelve Colonies (49 members)
- Two For Twilly (1 member)
- Unfinished Business (27 members)
- Unfinished Business (Extended Version) (1 member)
- Unfinished podcasts (56 members)
- Units of Distance (8 members)
- Units of Energy (3 members)
- Units of Mass (2 members)
- Units of Measure (25 members)
- Units of Time (9 members)
- Unproduced Scripts (17 members)
- Unproduced content (45 members)
- Unproduced content (1980) (13 members)
- Unproduced content (TOS) (30 members)
- Unvanquished (43 members)
- User warning templates (10 members)
- Usernames banned (5 members)
- Usernames under review (7 members)
- Users supporting the WGA strike (5 members)
- Users under warning (0 members)
- V-world Gamers (6 members)
- V-world gamers (1 member)
- VHS (3 members)
- Valley of Darkness (96 members)
- Video Game (74 members)
- Vipers (30 members)
- Vipers (RDM) (20 members)
- Vipers (TOS) (8 members)
- War of the Gods (7 members)
- War of the Gods, Part I (38 members)
- War of the Gods, Part II (30 members)
- Water (4,214 members)
- Weapons (23 members)
- Weapons (RDM) (6 members)
- Weapons (TOS) (8 members)
- Weapons (TRS) (3 members)
- Wikipedia (0 members)
- Wikipedians (1 member)
- Writers (61 members)
- Writers (1980) (4 members)
- Writers (Caprica) (6 members)
- Writers (RDM) (26 members)
- Writers (TOS) (8 members)
- Writers (TRS) (2 members)
- You Can't Go Home Again (46 members)