OSB may refer to:

• Oberstabsbootsmann, German Navy rank
• Old Saybrook station in Connecticut, USA (Amtrak station code)
• OneSavings Bank plc, a UK registered bank, trade name Kent Reliance
• Operation Sovereign Borders, Australian border security operation
• Operation Smiling Buddha, India's first successful nuclear bomb test (1974)
• Oracle Service Bus, a software communication system
• Oriented strand board, an engineered wood

• Oklahoma School for the Blind
• Open Source Business Alliance, sometimes known as OSB Alliance
• Oregon State Bar, public body that regulates the legal profession in Oregon, United States
• Orlando Solar Bears, ice hockey team in Florida
• Orquestra Sinfônica Brasileira, the Portuguese name of the Brazilian Symphony Orchestra

• 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