- Ondo State University of Science and Technology (Nigeria)
- One World University (Mozambique)
- Open International University for Alternative Medicines (India)
- Open Polytechnic (New Zealand)
- Open Slavic Law University (University Osyu) (Russia)
- Open University (United Kingdom)
- Open University Malaysia (Malaysia)
- Open University of Cyprus (Cyprus)
- Open University of Hong Kong (Hong Kong)
- Open University of Israel (Israel)
- Open University of Sri Lanka (Sri Lanka)
- Open University of Sudan (Sudan)
- Open University of Sudan (OUS) (Sudan)
- Open University of Tanzania (Tanzania)
- Open University of the Netherlands (Netherlands)
- Oradea University (Romania)
- Örebro University (Sweden)
- Orenburg State University (Russia)
- Oriental University (Russia)
- Oriental University Indore (India)
- Orissa University of Agriculture and Technology (India)
- Orkhon University (Mongolia)
- Osaka City University (Japan)
- Osaka College of Music (Japan)
- Osaka Dental University (Japan)
- Osaka Electro-Communication University (Japan)
- Osaka Gakuin University (Japan)
- Osaka Institute of Technology (Japan)
- Osaka International University (Japan)
- Osaka International University for Women (Japan)
- Osaka Medical College (Japan)
- Osaka Prefectural University (Japan)
- Osaka Sangyo University (Japan)
- Osaka Shoin Women's College (Japan)
- Osaka University (Japan)
- Osaka University of Arts (Japan)
- Osaka University of Commerce (Japan)
- Osaka University of Economics (Japan)
- Osaka University of Economics & Law (Japan)
- Osaka University of Education (Japan)
- Osaka University of Foreign Studies (Japan)
- Osaka University of Health and Sport Sciences (Japan)
- Osaka University of Pharmaceutical Sciences (Japan)
- Osaka Women's University (Japan)
- OSCE Academy in Bishkek (Kyrgyzstan)
- Oslo National Academy of Fine Arts (Norway)
- Oslo School of Architecture (Norway)
- Osmangazi University (Turkey)
- Osmania University, Hyderabad (India)
- Ostbayerische Technische Hochschule Regensburg (Germany)