Eponyms beginning with O
- O'Melmehey's triad
- Ober's abduction sign
- Ober's operation
- Ober's syndrome
- Ober's test
- Obersteiner-Redlich line
- Ober’s sign
- Obrinsky's syndrome
- Obrinsky-Fröhlich syndrome
- Ochsner's test
- Ochsner-Mahorner test
- Ochsner-Sherren treatment
- Oddi's sphincter
- Oddi's syndrome
- Odditis
- Ogilvie's syndrome
- Oguchi's disease
- Oguchi's syndrome
- Ohara's disease
- Okihiro's syndrome
- Okuda's needle
- Okuda-Chiba liver-biopsy needle
- Oliver's test (William Silver Oliver)
- Oliver-Cardarelli phenomenon
- Oliver-Cardarelli sign (William Silver Oliver)