- Obesity
- Obesity Research & Clinical Practice
- Obesity Reviews
- Obstetrics & Gynecology
- Obstetrics and Gynecology
- Occupational and Environmental Medicine
- Oceanography
- Oecologia
- Oikos
- Oncogene
- Oncogenesis
- OncoImmunology
- Oncotarget
- One Earth
- Open Biology
- Open Heart
- Operative Neurosurgery
- Ophthalmology
- Optica
- Optical Materials Express
- Optics and Lasers in Engineering
- Optics Express
- Optics Letters
- Optometry and Vision Science
- Organic Letters
- Organic Process Research & Development
- Organization Science
- Organization Studies
- Organizational Behavior and Human Decision Processes
- Oryx
- Osteoporosis International
- Oxford Economic Papers
- Oxford Journal of Archaeology