OSB may refer to:
- Orlando Solar Bears
- OSB, Amtrak station code for the Old Saybrook station in Connecticut, United States
- Oklahoma School for the Blind
- OneSavings Bank plc, a UK registered bank that operates under the trade name Kent Reliance
- Open Source Business Alliance, sometimes known as OSB Alliance
- Operation Smiling Buddha, code name for India's first successful test explosion of a nuclear bomb (1974)
- Oberstabsbootsmann, the highest non-commissioned officer rank in the German Navy
- Operation Sovereign Borders, Australian border security operation
- Oracle Service Bus, a software communication system made by Oracle Inc.
- Oregon State Bar, public body that regulates the legal profession in Oregon, United States
- Oriented strand board, an engineered wood
- Orquestra Sinfônica Brasileira, the Portuguese name of the Brazilian Symphony Orchestra
Christianity
- Order of Saint Benedict, Catholic monastic order
- Order of St Benedict (Anglican), Anglican monastic order
- Order of Saint Benedict (Orthodox), Orthodox monastic order
- Orthodox Study Bible, Eastern Orthodox Bible in English that includes the Septuagint