| Oryx | ORYX | 0030-6053 |
| Orzecznictwo Lekarskie | | 1732-8152 |
| Orzecznictwo Sądów Polskich | | |
| Orzecznictwo SadÓw Polskich | | |
| Orzecznictwo w Sprawach Samorządowych | ORZECZNICTWO W SPRAWACH SAMORZĄDOWYCH | 1232-7107 |
| Orđ Og Tunga | | 1022-4610 |
| OSA Continuum | OSA CONTINUUM | 2578-7519 |
| Osaka Journal of Mathematics | OSAKA J MATH | 0030-6126 |
| Osgoode Hall Law Journal | OSGOODE HALL LAW JOURNAL | 0030-6185 |
| Osiris | OSIRIS | 0369-7827 |
| Oslo Law Review | OSLO LAW REVIEW | 2387-3299 |
| Osmanli Arastirmalari-The Journal of Ottoman Studies | OSMANLI ARASTIRMALARI-THE JOURNAL OF OTTOMAN STUDIES | 0255-0636 |
| Osmanli Bilimi Arastirmalari (studies in Ottoman Science) | | 1303-3123 |
| Osmanlı Mirası Araştırmaları Dergisi | OSMANLI MIRASI ARAŞTIRMALARI DERGISI | 2148-5704 |
| Osnabrücker Beiträge Zur Sprachtheorie (obst) | | 0936-0271 |
| Osong Public Health and Research Perspectives | OSONG PUBLIC HEALTH AND RESEARCH PERSPECTIVES | 2210-9099 |
| Osservatorio del Diritto Civile e Commerciale | OSSERVATORIO DEL DIRITTO CIVILE E COMMERCIALE | 2281-2628 |
| Ostasiatische Zeitschrift | | 1617-9404 |
| Osteoarthritis and Cartilage | OSTEOARTHR CARTILAGE | 1063-4584 |
| Osteologicky Bulletin | OSTEOLOGICKY BULLETIN | 1211-3778 |
| Osteologie | OSTEOLOGIE | 1019-1291 |
| Osteopathic Family Physician | OSTEOPATHIC FAMILY PHYSICIAN | 1877-573X |
| Osteoporosis and Sarcopenia | OSTEOPOROSIS AND SARCOPENIA | 2405-5255 |
| Osteoporosis International | OSTEOPOROSIS INT | 0937-941X |
| Osterreichische Musikzeitschrift | OSTERREICHISCHE MUSIKZEITSCHRIFT | 0029-9316 |
| Österreichische Namenforschung | | 1028-1495 |
| Österreichische Osthefte | | 0029-9375 |
| Osterreichische Zeitschrift fuer Soziologie | OSTERREICHISCHE ZEITSCHRIFT FUER SOZIOLOGIE | 1011-0070 |
| Osterreichische Zeitschrift fur Geschichtswissenschaften | | 1016-765X |
| Österreichische Zeitschrift Für Kunst und Denkmalpflege | | 0029-9626 |
| Osterreichische Zeitschrift fur Politikwissenschaft | OSTERR Z POLITWISS | 1615-5548 |
| Osterreichische Zeitschrift fur Volkskunde | | 0029-9669 |
| Osterreichisches Archiv fur Recht und Religion | | 1560-8670 |
| Osterreichisches Religionspadagogisches Forum | OSTERREICHISCHES RELIGIONSPADAGOGISCHES FORUM | 1018-1539 |
| Osteuropa | OSTEUROPA | 0030-6428 |
| Ostkirchliche Studien | | 0030-6487 |
| Ostomy Wound Management | OSTOMY WOUND MANAG | 0889-5899 |
| Ostraka | | 1122-259X |
| Ostrich | OSTRICH | 0030-6525 |
| Ostry Dyżur | | 1898-3316 |
| OT Practice | OT PRACTICE | 1084-4902 |
| OTJR Occupation, Participation and Health | OTJR-OCCUP PART HEAL | 1539-4492 |
| Oto-Rhino-Laryngology Tokyo | OTO-RHINO-LARYNGOLOGY TOKYO | 0386-9687 |
| Polish Journal of Otolaryngology | | 0030-6657 |
| Otolaryngologia Polska / Polish Journal of Otolaryngology | | |
| Otolaryngologic Clinics of North America | OTOLARYNG CLIN N AM | 0030-6665 |
| Otolaryngology - Head and Neck Surgery (Tokyo) | OTOLARYNGOLOGY - HEAD AND NECK SURGERY (TOKYO) | 0914-3491 |
| Otolaryngology Case Reports | OTOLARYNGOLOGY CASE REPORTS | 2468-5488 |
| Otolaryngology - Head and Neck Surgery | OTOLARYNG HEAD NECK | 0194-5998 |
| Otology and Neurotology | OTOL NEUROTOL | 1531-7129 |
