Isaar or ISAAR may refer to:

• Isaar, Wisconsin, an unincorporated community in the USA
• International Standard Archival Authority Record, or ISAAR, a form of authority control record

• Acta of the Apostles
• Acta oncologica (Stockholm, Sweden)
• Acta Ophthalmol.
• Acta Ophthalmol
• Acta Ophthalmologica
• Acta Ophthalmologica Scandinavica
• Acta Ophthalmologica Scandinavica Foundation
• Acta Ophthalmol. Scand.
• Acta Ophthalmol Scand
• Acta Paediatrica (Oslo, Norway : 1992)
• Acta paediatrica (Oslo, Norway : 1992)
• Acta paediatrica (Oslo, Norway : 1992). Supplement
• Acta paediatrica Scandinavica
• Acta paediatrica. Supplementum
• Acta Paediatr Scand.
• Acta Paediatr Scand
• Acta palaeontologica Polonica
• Acta Pauli
• Acta Pauli et Theclae
• Acta Philosophica
• Acta Phys.
• Acta Phys
• Acta Physica
• Acta Physica Hungarica
• Acta Physica Sinica