Altair (Alpha Aquilae / Alpha Aql / α Aquilae / α Aql / Atair) is the brightest star in the constellation Aquila and the twelfth brightest star in the night sky. It is an A-type main sequence star with an apparent visual magnitude of 0.77 and is one of the vertices of the Summer Triangle; the other two are Deneb and Vega.

Altair rotates rapidly, with a velocity at the equator of around 286 km/s. A groundbreaking study with the Palomar Testbed Interferometer revealed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation. Synthetic aperture techniques with multiple telescopes, operating in the infrared, have imaged this phenomenon.