Crux, or the Southern Cross, is a constellation in the southern hemisphere. It is the smallest of the 88 constellations, but also among the brightest, which makes it one of the best known constellations in the southern sky. Its name means "cross" in Latin.
Crux, with its prominent cross-like asterism, is represented on the flags of several countries, including Australia, Brazil and New Zealand. Ancient Greeks considered the stars of Crux to be part of the constellation Centaurus
. By the year 400 CE, Crux dropped below the horizon for Greece and most of Europe and was not rediscovered on the continent until Amerigo Vespucci mapped it while travelling to South America in 1501. In the 17th century, the French astronomer Augustin Royer separated the constellation from Centaurus
. Crux' status as a constellation in its own right is also often attributed to the Dutch astronomer Petrus Plancius.
Crux has great cultural significance in southern latitudes. Several Aboriginal cultures see Crux and the Coalsack Dark Nebula as the head of the "Emu in the sky," while to others it represents the sky deity Mirrabooka. Before invaders took away the land from the tribes and renamed the constellation to "Southern Cross," Crux was called Mirrabooka, after the wise man whom Biami, an important male Spirit Ancestor in the tales of the tribes of south-eastern Australia, had chosen to help him watch over the tribes. It is said that Biami gave the man lights for his hands and feet and placed him among the stars. The Maori in New Zealand called the cross Te Punga ("the anchor").
The cross is represented in South American cultures as well. An image of the constellation was found carved in stone in Machu Picchu, Peru. The name was also documented in Mapudungun, the language of Patagonian Mapuches, who called it Melipal ("four stars"), while the Incas called the constellation Chakana ("stair"). Even in the northern hemisphere, some find religious symbolism in the disappearance of the constellation under the horizon, linking it to the crucifixion of Christ.
The constellation Crux occupies an area of 68 square degrees and contains one star with known planets. It can be seen at latitudes between +20° and -90° and is best visible at 9 p.m. during the month of May.
The principal star in Crux is 
alpha Crucis, also known as Acrux (contraction of "alpha" and "Crux"), a binary star about 360 light-years distant. It is the twelfth brightest star in the sky, with a visual magnitude 0.77. The two discernible components of the binary are both hot class B bright blue stars.
beta Crucis, also known as Mimosa (because of its colour) or Becrux, is the brightest star in Crux and also among the brightest stars in the sky. It is a blue-white giant visible only south of the Tropic of Cancer. The Chinese know it as the Third Star of the Cross.
The third brightest star in the constellation, 
gamma Crucis, or Gacrux, is a binary star consisting of a red giant 88 light-years distant and an optical white companion star 400 light-years away from Earth.
delta Crucis, or Palida in Portuguese, is a subgiant and a Beta Cephei variable, changing its brightness within a period of 1.3 hours. Its rotation period is relatively short, less than 1.3 days.
Crux has several notable deep sky objects. NGC 4755, also known as the Kappa Crucis star cluster or the Jewel Box, is an open cluster that consists of more than a hundred stars. About half of them are supergiants, red, blue, yellow and white. The central star of the Kappa Crucis cluster, 
kappa Crucis, is a magnitude 6 blue supergiant
Crux contains the famous Coalsack Nebula, a dark silhouette in the sky that stands in stark contrast against the Milky Way. Lying approximately 600 light-years away from Earth, the Coalsack is the most prominent dark nebula in the sky, along with the Horsehead Nebula in the constellation Orion.
Crux belongs to the Hercules family of constellations, along with Hercules
, Corona Australis
and Triangulum Australe
Constellations directly bordering Crux are Centaurus