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| Institution | Country | Rankings | ||
|---|---|---|---|---|
| Ohio University | US | S | ||
| Ohio State University | US | Q S T | ||
| Okayama University | JP | Q S | ||
| University of Oklahoma | US | Q S T | ||
| Oklahoma State University | US | S | ||
| Old Dominion University | US | S T | ||
| Open University | UK | Q S | ||
| University of Oregon | US | Q S T | ||
| Oregon Health and Science University | US | S | ||
| Oregon State University | US | Q S T | ||
| School of Oriental and African Studies, University of London | UK | Q | ||
| Osaka University | JP | Q S T | ||
| Osaka City University | JP | Q S | ||
| Osaka Prefectural University | JP | S | ||
| University of Oslo | NO | L Q S T | ||
| University of Otago | NZ | Q S T | ||
| University of Ottawa | CA | Q S T | ||
| Otto-von-Guericke Universität Magdeburg | DE | L | ||
| University of Oulu | FI | L Q S | ||
| University of Oviedo | ES | L S | ||
| University of Oxford | UK | L Q S T |