ONS may stand for:
- Occipital nerve stimulation
- ONS coding system
- Oral Nutritional Supplements
- The Ons Island in Galicia, Spain.
- Oberste Nationale Sportbehörde, former German motor racing governing body, now Deutscher Motor Sport Bund (DMSB)
- Object Naming Service
- Office National des Statistiques de l'Algérie
- Office for National Statistics, UK
- One-name study, the study of a single surname
- One night stand
- (WWE) One Night Stand
- Order of Nova Scotia (Canadian decoration post-nominal letters)
- Old North State Council of the Boy Scouts of America
- Original Night Stalker, unidentified serial killer and rapist also known as East Area Rapist
- Oncology Nursing Society
- The IATA airport code for Onslow Airport in Western Australia