Aldebaran, the bull's-eye (α Tau / alpha Tauri), is the brightest star in the constellation Taurus and one of the brightest stars in the nighttime sky. It is the sun in the Arabian mythology .

Its name is derived from Arabic الدبران ad-dabarān meaning "the follower", a reference to the way the star follows the Pleiades star cluster in its nightly journey across the sky. Aldebaran itself has the appearance of being the brightest member of the more scattered Hyades cluster, which is the closest star cluster to Earth. However, it is merely located in the line of sight between the Earth and the Hyades, and is actually an independent star.

Aldebaran is a K5 III star, which means it is orangish, large, and has moved off of the main sequence by using all its hydrogen fuel. It has a minor companion (a dim M2 dwarf orbiting at several hundred AU). Now primarily fusing helium, the main star has expanded to a diameter of approximately 5.3 × 10⁷ km, or about 38 times the diameter of the Sun. The Hipparcos satellite has measured it as 65.1 light years away, and it shines with 150 times the Sun's luminosity. Taken together this distance and brightness makes it the 13th brightest star in the sky. It is slightly variable, of the pulsating variable type, by about 0.2 magnitude.

In 1997, a possible large planet (or small brown dwarf) companion was reported, with a minimum mass of 11 Jupiters and orbiting at a distance of 1.35 AU.

Astrologically, Aldebaran was a fortunate star, portending riches and honor. This star is one of the four "royal stars" of the Persians from around 3000 BC. In the religion of Stregheria, Aldebaran is a fallen angel and quarter guardian of the eastern gate .

Aldebaran is one of the easier stars to find in the night sky, partly due to its brightness and partly due to its spatial relation to one of the more noticeable asterisms in the sky. If one follows the three stars of Orion's belt from left to right (in the Northern Hemisphere) or right to left (in the Southern), the first bright star found by continuing that line is Aldebaran.