There are 1,912 titles that begin with the letter O
- Opera Canada (ISSN: 0030-3577, )
- Opera Corcontica (ISSN: 0139-925X, 1803-1412)
- Opera Historica (ISSN: 1805-790X, 2694-720X)
- The Opera journal (ISSN: 0030-3585, )
- Opera News (ISSN: 0030-3607, 1938-1506)
- The Opera Quarterly (ISSN: 0736-0053, 1476-2870)
- Opera slavica (ISSN: 1211-7676, 2336-4459)
- Opera Software ASA MarketLine Company Profile (ISSN: )
- Operant subjectivity (ISSN: 0193-2713, )
- The operating theatre journal (ISSN: 1747-728X, )
- Operation County fair Newsletter (ISSN: )
- Operational Research (ISSN: 1109-2858, 1866-1505)
- Operational Research in Engineering Sciences: Theory and Applications (ISSN: 2620-1607, 2620-1747)
- Operational Research Quarterly (1950-1952) (ISSN: 1473-284X, 2397-5350)
- Operational Research Quarterly (1970-1977) (ISSN: 0030-3623, 2397-5334)
- Operational Risk & Regulation (ISSN: 2045-0672, )
- Operations Management (ISSN: 1529-5648, )
- Operations Management Education Review (ISSN: 1649-7082, 2044-4567)
- Operations Management Research (ISSN: 1936-9735, 1936-9743)
- Operations report / Franchise Tax Board (ISSN: )
- Operations Research (ISSN: 0030-364X, 1526-5463)
- Operations Research and Decisions (ISSN: 2081-8858, )
- Operations Research for Health Care (ISSN: 2211-6923, 2211-6931)
- Operations Research Forum (ISSN: , 2662-2556)
- Operations Research Letters (ISSN: 0167-6377, 1872-7468)
- Operations Research Perspectives (ISSN: 2214-7160, )
- Operative dentistry (ISSN: 0361-7734, 1559-2863)
- Operative Neurosurgery (ISSN: 2332-4252, 2332-4260)
- Operative Orthopadie und Traumatologie (ISSN: 0934-6694, 1439-0981)
- Operative techniques in cardiac & thoracic surgery (ISSN: 1085-5637, 1876-4770)
- Operative techniques in general surgery (ISSN: 1524-153X, 1558-383X)
- Operative techniques in neurosurgery (ISSN: 1092-440X, 1557-9409)
- Operative techniques in orthopaedics (ISSN: 1048-6666, 1558-3848)
- Operative techniques in otolaryngology--head and neck surgery (ISSN: 1043-1810, 1557-9395)
- Operative techniques in plastic and reconstructive surgery (ISSN: 1071-0949, 1558-0741)
- Operative Techniques in Sports Medicine (ISSN: 1060-1872, 1557-9794)
- Operative techniques in thoracic and cardiovascular surgery (ISSN: 1522-2942, 1532-8627)
- Opérations de l'année (ISSN: )
- Opérations de l'année (ISSN: )
- Opflow (ISSN: 0149-8029, 1551-8701)
- Ophthalmic and Physiological Optics (ISSN: 0275-5408, 1475-1313)
- Ophthalmic Epidemiology (ISSN: 0928-6586, 1744-5086)
- Ophthalmic Genetics (ISSN: 1381-6810, 1744-5094)
- Ophthalmic paediatrics and genetics (ISSN: 0167-6784, )
- Ophthalmic Plastic and Reconstructive Surgery (ISSN: 0740-9303, 1537-2677)
- Ophthalmic Research (ISSN: 0030-3747, 1423-0259)
- Der Ophthalmologe (ISSN: 0941-293X, 1433-0423)
- Ophthalmologica Extra (ISSN: , 2296-1445)
- Ophthalmologie (ISSN: 2731-720X, 2731-7218)
- Ophthalmology (ISSN: 0161-6420, 1549-4713)
- Ophthalmology and Eye Diseases (ISSN: , 1179-1721)
- Ophthalmology and Therapy (ISSN: 2193-8245, 2193-6528)
- Ophthalmology Journal (ISSN: 2450-7873, 2450-9930)
- Ophthalmology Science (ISSN: 2666-9145, )
- Ophthalmology Times (ISSN: 0193-032X, 2150-7333)
- Ophthalmology Update (ISSN: 1993-2863, )
- Opinio Juris in Comparatione (ISSN: 2036-4423, 2281-5147)
- Opinion publique (ISSN: )
- Opinion publique : journal illustré (ISSN: )
- Opinions (ISSN: 1756-7629, )
- Opinions of the Office of Legal Counsel of the United States Department of Justice (ISSN: 0270-2134, )
- Opinião Pública (ISSN: 0104-6276, 1807-0191)
- La Opinión (ISSN: 0276-590X, )
- La Opinión de A Coruña (ISSN: 1576-8694, )
- Opinión Jurídica (ISSN: 1692-2530, 2248-4078)
- Oplink Communications, Inc. MarketLine Company Profile (ISSN: )
- Opolis (ISSN: 1552-2148, 1551-5869)
- Opolskie Studia Administracyjno-Prawne (ISSN: 1731-8297, 2658-1922)
- Oppdragsrapport. A - Norges vassdrags- og energidirektorat (ISSN: 1503-0318, )
- Oppenheimer Holdings Inc. MarketLine Company Profile (ISSN: )
- Oppervlaktetechnieken (ISSN: 1571-9995, )
- Opportunistic pathogens (ISSN: 1386-2618, 1878-3694)
- Opportunities for Research in Renaissance Drama (ISSN: 2378-4016, 2380-1166)
- Opportunities for Research in Renaissance Drama (Exclusive of Shakespeare) (ISSN: 2378-3990, 2380-1182)
- Opportuun : tijdschrift voor het Openbaar Ministerie (ISSN: 1380-3913, )
- The Oppressed (ISSN: )
- OPSEARCH (ISSN: 0030-3887, 0975-0320)
- OPSI (ISSN: 1693-2102, 2686-2352)
- Optica (ISSN: 2334-2536, )
- OPTICA APPLICATA (ISSN: 0078-5466, 1899-7015)
- Optical and Quantum Electronics (ISSN: 0306-8919, 1572-817X)
- Optical Cable Corporation MarketLine Company Profile (ISSN: )
- Optical Data Processing and Storage (ISSN: , 2084-8862)
- Optical Engineering (ISSN: 0091-3286, 1560-2303)
- Optical Fiber Communication (OFC)Conference (ISSN: )
- Optical Fiber Technology (ISSN: 1068-5200, 1095-9912)
- Optical Interconnects Conference, IEEE (ISSN: 2376-8665, )
- Optical Materials (ISSN: 0925-3467, 1873-1252)
- Optical Materials Express (ISSN: 2159-3930, )
- Optical Materials: X (ISSN: , 2590-1478)
- Optical Memory & Neural Networks (ISSN: 1060-992X, 1934-7898)
- Optical Memory News (ISSN: 0741-5869, )
- Optical MEMS, IEEE/LEOS International Conference on (ISSN: 2160-5033, 2160-5041)
- Optical Nanoscopy (ISSN: 2192-2853, )
- Optical Review (ISSN: 1340-6000, 1349-9432)
- Optical Switching and Networking (ISSN: 1573-4277, 1872-9770)
- Optician (ISSN: 0030-3968, 2632-0010)
- Opticon1826 (ISSN: 2049-8128, )
- Optics (ISSN: , 2673-3269)
- Optics & photonics focus (ISSN: 2013-1445, )