Sigourney Weaver (born Susan Alexandra Weaver; October 8, 1949) is an American actress. She is known especially for the lead role of Ellen Ripley in the four Alien films: Alien, Aliens, Alien 3 and Alien Resurrection. She is also well known for her roles in Ghostbusters and Ghostbusters II, Gorillas in the Mist, Working Girl, and Avatar.