- Obafemi Awolowo University
- Omnitor AB
- OneSource, Consultoria Informática Lda. [Coimbra]
- Open Universiteit Nederland [Heerlen]
- Open University of Cyprus
- Open University of the Netherlands [Heerlen]
- Orange Communications SA
- Orange Labs [Lannion]
- Oregon State University
- Osaka Prefecture University
- Osaka University
- Osaka University [Osaka]
- Oslo Metropolitan University
- Oticon A|S [Danemark]
- Otto-von-Guericke-Universität Magdeburg = Otto-von-Guericke University [Magdeburg]
- Oulu University of Applied Sciences
- Oxford Brookes University
- Oxford University Computing Laboratory
- Oxford e-Research Centre [Oxford]
- Örebro University