An Air Data Inertial Reference Unit (ADIRU) is a key component of the integrated Air Data Inertial Reference System (ADIRS), that supplies air data (airspeed, angle of attack and altitude) and inertial reference (position and attitude) information to the pilots' Electronic Flight Instrument System displays as well as other systems on the aircraft such as the engines, autopilot, flight control and landing gear systems. An ADIRU acts as a single, fault tolerant source of navigational data for both pilots of an aircraft. It may be complemented by a Secondary Attitude Air Data Reference Unit (SAARU), as in the Boeing 777 design.

This device is used on various military aircraft as well as civilian airliners starting with the Airbus A320 and Boeing 777.