Sigourney Weaver (born Susan Alexandra Weaver; October 8, 1949) is an American actress. She is known especially for her role of Ellen Ripley in the four Alien films: Alien, Aliens, Alien 3, and Alien Resurrection. Other notable roles include Dana Barrett in Ghostbusters and its sequel Ghostbusters II, Gorillas in the Mist: The Story of Dian Fossey Working Girl, The Ice Storm, Galaxy Quest, Prayers for Bobby and GraceAugustine in Avatar.