Extraterrestrial life is creatures or species that, on theories, exist and develop outside the Earth.

Most scientists believe that if extraterrestrial life exists, its evolution would have appeared independently in many different places in the universe. There is another theory that extraterrestrial life may have a common origin, and then disperse throughout the universe, from one habitable planet to another habitable planet. There is another suggestion that if we find extraterrestrial life and civilization near us, that life and civilization are either much more developed than us or still much more primitive than us.