- Office of Strategic Influence
- Office of Strategic Influence (band)
- Office of Strategic Influence (album)
- Ontario Swine Improvement
- Open Systems Interconnection, a joint ISO and ITU-T standard for computer networks and protocols.
- Open Source Initiative
- OSI model
- Ordnance Survey Ireland (Suirbhéireacht Ordanáis Éireann)
- Origin Systems, Inc, a computer game developer
- There are also a number of organizations known as the "Office of Special Investigations":
- The U.S. DOJ Office of Special Investigations which detects and investigates individuals in the U.S. who took part in Nazi-sponsored acts of persecution abroad before and during World War II
- The U.S. Air Force Office of Special Investigations
- The U.S. GAO Office of Special Investigations