COI
- California Oregon Intertie
- Center on Organizational Innovation
- Central Office of Information
- Centre of inertia
- Certificate of incorporation
- Certificate of insurance
- Church of Ireland
- Coefficient of Inbreeding
- Coi (album)
- Coi (restaurant)
- College of Idaho
- Commission de l'Océan Indien
- Commission of inquiry (disambiguation)
- Community of inquiry
- Community of interest (computer security)
- Comoros
- Confirmed opt-in
- Conflict of interest
- Constitution of India
- Contingency Orbit Insertion
- Coy (disambiguation)
- Cytochrome Oxidase Subunit 1
- Dennis Coi
- Disease burden
- Koi (disambiguation)
- Trịnh Cối
- Xeon Phi