Alcyone is a star system in the constellation Taurus. It is the brightest star in the Pleiades open cluster. Alcyone is approximately 440 light years from Earth. The primary component, Alcyone A, is a blue-white B-type giant with an apparent magnitude of +2.85. It is an eclipsing binary, and the two components have a separation of 0.031 arcseconds, or about the distance from the Sun to Jupiter. Alcyone A has a luminosity of 1,400 times that of the Sun and a temperature of almost 13,000 K. The spectral type of B7 IIIe indicates that it is an emission star. A high rotational velocity of some 215 km/s has created a disk of gases flung into orbit around the star from its equator.

The binary star is orbited by three companions. Alcyone B and Alcyone C are both 8th magnitude white A-type dwarfs. Alcyone D is a yellow-white F-type dwarf Alcyone C is classified as a Delta Scuti type variable star and its brightness varies from magnitude +8.25 to +8.30 over 1.13 hours.

In Star Trek, the Alcyones are a spacefaring civilization that destroyed what was believed, by the Federation, to be the last Tarellian plague vessel in 2356. It was later discovered that the ship they destroyed was not the last plague ship, following the discovery of another such vessel in the Beta Cassius system in 2364. (TNG: "Haven")