Oga or OGA may refer to:
- Oga, Akita, Japan
- Oga Peninsula
- Oga, a frazione of Valdisotto, Italy
- Oga Atsushi, a Japanese sumo wrestler
- OGA, Other government agency, i.e. the American CIA or its counterparts in other countries
- Office Genuine Advantage in Microsoft Office
- Ogg, An Ogg file containing audio
- Open Genealogy Alliance
- Oregon Golf Association
- OGA, the IATA airport code for Searle Field airport, Ogallala, Nebraska