The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- 1996 home game consoles (1 member)
- 1998 home game consoles (1 member)
- 2001 home game consoles (1 member)
- 2006 video games (1 member)
- 2011 video games (1 member)
- 21st-century male musicians from the United States (1 member)
- 3D computer graphics (1 member)
- 3D models (0 members)
- Academic disciplines by topic (1 member)
- Activities (2 members)
- Android video games by name (1 member)
- Art-related icons (1 member)
- Autotranslated templates (1 member)
- Beryl (window manager) (0 members)
- Biology (0 members)
- Biology navigational templates (2 members)
- Biology templates (1 member)
- Black and white flags (1 member)
- Blue circle icons (1 member)
- Blue circle info icons (0 members)
- Blue info icons (1 member)
- Boreoeutheria (0 members)
- CC-BY-SA-3.0-US (1 member)
- CC-Zero (1 member)
- CC license tags (2 members)
- Caniformia (0 members)
- Card game publishing companies (1 member)
- Carnivora (1 member)
- Carnivoraformes (1 member)
- Carnivoramorpha (1 member)
- CatAutoTOC generates no TOC (1 member)
- Categories by name (flat list) (1 member)
- Categories lacking description (1 member)
- Categories of biology requiring diffusion (1 member)
- Categories requiring diffusion (1 member)
- Categories requiring permanent diffusion (2 members)
- Categories requiring permanent diffusion to zero (5 members)
- Category TOC templates (3 members)
- Category navigational templates (2 members)
- Cave game tech test (6 members)
- Cellular organisms (1 member)
- Cereal-based food (1 member)
- Cereal products (1 member)
- Circle info icons (1 member)
- Classification (1 member)
- Classification systems (0 members)
- CommonsRoot (1 member)
- Commons templates-en (15 members)
- Commons templates-i18n (2 members)
- Commons utility templates (1 member)