- Obninsk State Technical University for Nuclear Power Engineering (Russia)
- Oda Bultum University (Ethiopia)
- Odessa National Academy of Food Technologies (Ukraine)
- Odessa National I.I. Mecnikov University (Ukraine)
- Odessa National Marine University (Ukraine)
- Odessa National Maritime Academy (Ukraine)
- Odessa National Polytechnic University (Ukraine)
- Odessa State Medical University (Ukraine)
- Odlar Yurdu University (Azerbaijan)
- Oita Medical University (Japan)
- Oita University of Nursing and Health Sciences (Japan)
- Okanagan University College (Canada)
- Okan University (Turkey)
- Okayama Prefectural University (Japan)
- Okinawa Institute of Science and Technology Graduate University (OIST) (Japan)
- Okinawa International University (Japan)
- Okinawa Prefectural University of Fine Arts (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 Medicical Academy (Russia)
- Omsk State Pedagogical University (Russia)
- Omsk State Technical University (Russia)
- onal Taipei University of Nursing and Health Sciences (Taiwan)
- 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 Israel (Israel)
- Open University of Sri Lanka (Sri Lanka)
- Open University of Tanzania (Tanzania)
- Open University of the Netherlands (Netherlands)
- Oriental University (Russia)
- Oriental University Indore (India)
- Orissa University of Agriculture and Technology (India)
- Orkhon University (Mongolia)
- Osaka College of Music (Japan)
- Osaka Dental University (Japan)
- Osaka Electro-Communication 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)