OSF may stand for:
- Ógra Shinn Féin, the youth wing of the Sinn Féin political party
- Old style figures
- Open Software Foundation
- Operational Support Facility
- Opera Show Format, an XHTML-based slideshow format
- Ordered-Sorted Feature Logic, a logic formalism
- Oregon Shakespeare Festival repertory theatre in Ashland, Oregon
- Oxford Scientific Films
- The Old Spaghetti Factory
- Independent Senate Fraction or Onafhankelijke Senaatsfractie, a political group of the Netherlands
- Order of Servant Franciscans, a Franciscan order
- Oklahoma Office of State Finance - an agency of the Government of Oklahoma responsible for centralized State government budgeting and accounting
- Old School Fighters