Encyclopedias, Almanacs, Transcripts, and Maps
- Oscilloclast
- Osis, Karlis (1917-1997)
- Oskar Morgenstern
- Oskar Wilhelm August Hertwig
- Osler-Weber-Rendu syndrome
- Osler-Weber-Rendu Syndrome
- Osmond Fisher
- Osmond, Humphrey (Fortescue)
- Osmont, Anne (1872-1953)
- Osmosis (Cellular)
- Osmosis (Cellular)
- Ossowiecki, Stephan (1877-1944)
- Osteology and Skeletal Radiology
- Osteoporosis Diet
- Ostrich: Struthionidae
- Osty, Eugèn (1874-1938)
- Oswald Veblen
- Otani, Soji (1924-)
- Otis Barton b
- Otis Boykin