- Odlar Yurdu University (Azerbaijan)
- Oduduwa University (Nigeria)
- Ohka Gakuen University (Japan)
- Ohtani Women's University (Japan)
- Ohu University (Japan)
- Oita Medical University (Japan)
- Oita University (Japan)
- Oita University of Nursing and Health Sciences (Japan)
- Okanagan University College (Canada)
- Okan University (Turkey)
- Okayama Prefectural University (Japan)
- Okayama Shoka University (Japan)
- Okayama University (Japan)
- Okayama University of Science (Japan)
- Okinawa Institute of Science and Technology Graduate University (OIST) (Japan)
- Okinawa International University (Japan)
- Okinawa Prefectural University of Fine Arts (Japan)
- Okinawa University (Japan)
- Olabisi Onabanjo University (Nigeria)
- Olympia College (Malaysia)
- Oman College Of Management & Technology (Oman)
- Omar Al-Mukhtar University (Libya)
- Omdurman Ahlia University (Sudan)
- Omdurman Islamic University (Sudan)
- Omsk State Agrarian University (Russia)
- Omsk State Medicical Academy (Russia)
- Omsk State Pedagogical University (Russia)
- Omsk State Technical University (Russia)
- Omsk State Transport University (Russia)
- Omsk State University (Russia)
- onal Taipei University of Nursing and Health Sciences (Taiwan)
- Ondokuz Mayis University Samsun (Turkey)
- 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)