Grey aliens, also referred to as Zeta Reticulans, Roswell Greys, or simply, Greys, are purported extraterrestrial beings. They are frequently featured in claims of close encounter and alien abduction. Greys are typically described as having small, humanoid bodies, smooth, grey skin, disproportionately large, hairless heads, and large, black, almond-shaped eyes.

The 1961 Barney and Betty Hill abduction claim was key to the popularization of Grey aliens. Precursor figures have been described in science fiction and similar descriptions appeared in later accounts of the 1947 Roswell UFO incident and early accounts of the 1948 Aztec UFO hoax.

The Grey alien is cited an archetypal image of an intelligent non-human creature and extraterrestrial life in general, as well as an iconic trope of popular culture in the age of space exploration.