Grey aliens, also referred to as Zeta Reticulans, Roswell Greys or Greys, are purported extraterrestrial beings. They are frequent subjects of close encounters and alien abduction claims. The details of such claims vary widely. That said, Greys are typically described as being human-like with small bodies, smooth, grey-colored skin; enlarged, hairless heads; and large, black eyes. The Barney and Betty Hill abduction claim, which purportedly took place in New Hampshire in 1961, popularized Grey aliens. Precursor figures have been described in science fiction and similar descriptions appeared in early accounts of the 1948 Aztec UFO hoax and later accounts of the 1947 Roswell UFO incident.

The Grey alien has emerged as 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.