IAR may refer to:

• IAR Systems, an embedded system technology company
• A former stock market ticker for Idearc Media, a communications company
• The Institute of Asian Research, an institute under the Faculty of Arts in the University of British Columbia, Vancouver, BC, Canada
• "Ignore all rules", a self-contradictory rule
• Industria Aeronautica Româna (IAR Brasov), an aerospace manufacturer
• M27 Infantry Automatic Rifle, a new weapon design commissioned by the U.S. Marine Corps
• Instruction address register, an alternative name for the program counter CPU register
• International Authority for the Ruhr, an organization in control of the industry in the Ruhr area from 1949 to 1952
• International Affairs Review, an academic journal in the field of international affairs
• Informacyjna Agencja Radiowa, a Polish news agency

• The IATA code for the Tunoshna Airport, Yaroslavl Oblast, Russia
• .iar, Inventory ARchive file used for avatar inventory backup in OpenSimulator virtual environments

Íar mac Dedad (Íar, son of Deda mac Sin) was a legendary King of Munster. He is the father, or in some sources more distant ancestor, of Eterscél Mór, and grandfather (or great-grandfather) of the famous Conaire Mór, both High Kings of Ireland.