- Oberhessische Geologische Abhandlungen
- Oberhessische Naturwissenschaftlichen Zeitschrift
- Occasional Paper
- Occasional Paper from the Museum Victoria
- Oceanus
- Oceanus. Reports on Research from the Woods Hole Oceanographic Institution
- Oceanus. Annual Report of the Woods Hole Ocenographic Institution
- Ochrona Przyrody
- Ofioliti. Bolletino del Grupo di Lavoro sulle Ofioliti Mediterranee
- Oklahoma Geology Notes
- Original Report of the Okamura Fossil Laboratory
- Österreichische Akademie der Wissenschaften Schriftenreihe der Erdwissenschaftlichen Kommissionen
- Otečestvennaja Geologija
- Overseas Geology and Mineral Resources
- Overseas Geology and Mineral Resources, Supplement Series Bulletin Supplement
- Overseas Memoir
- Översiktskarter med Beskrivningar Serie Ba