OSB
- Brazilian Symphony Orchestra
- Kent Reliance
- Oberstabsbootsmann
- Oklahoma School for the Blind
- Old Saybrook station
- Open Source Business Alliance
- Operation Smiling Buddha
- Operation Sovereign Borders
- Oracle Service Bus
- Order of Saint Benedict
- Order of Saint Benedict (Orthodox)
- Order of St Benedict (Anglican)
- Oregon State Bar
- Oriented strand board
- Orlando Solar Bears
- Orthodox Study Bible