Oi
- Aussie Aussie Aussie, Oi Oi Oi
- Gha
- Grey-faced petrel
- Hoy (disambiguation)
- Iwan Fals
- Japanese cruiser Ōi
- List of Latin-script digraphs
- O-I
- Oi (general)
- Oi (interjection)
- Oi (telecommunications)
- Oi Oi Oi (album)
- Oi language
- Oi!
- Oi! (Hong Kong)
- Oi! (song)
- Operating income
- Organizational intelligence
- Organoid intelligence
- Oriental Institute (disambiguation)
- Orphans International
- Orthostatic intolerance
- Osteogenesis imperfecta
- Oy (disambiguation)
- Ōi (disambiguation)