Biowissenschaften, Biologie
- Oceanological and hydrobiological studies
- Oceanus
- Oecologia
- Oikos : a journal of ecology
- Open life sciences
- Ophelia : international journal of marine biology
- Optik : international journal for light and electron optics ; in affiliation with the European Optical Society ; official organ of the German Society of Applied Optics
- Orchids : the bulletin of the American Orchid Society
- Organic & biomolecular chemistry : OBC
- Organic & biomolecular chemistry : OBC ; an international journal of synthetic, physical and biomolecular organic chemistry
- Organic electronics : materials, physics, chemistry, applications
- Organisms, diversity & evolution : journal of the Gesellschaft für Biologische Systematik (GfBS)
- Organogenesis
- Oriental insects : a journal of systematic entomology and zoogeography of South and South-East Asia
- Origins of life and evolution of biospheres : the journal of the International Astrobiology Society
- Österreichische botanische Zeitschrift
- Österreichische botanische Zeitschrift
- Outlooks on pest management : the management of weeds, pests and diseases through chemistry, biology and biotechnology