Sigourney Alexandra Weaver (born October 8, 1949) is an American actress. She is best known for her roles as Lieutenant Ellen Ripley in the Alien film series and as Dana Barrett in the Ghostbusters movies. Weaver is also a three-time Academy Award nominee for her performances in Aliens, Gorillas in the Mist and Working Girl. She is one of the very few actresses who has been nominated for an Academy Award for Best Actress for her role in a science fiction movie (Aliens).

Weaver was born Susan Alexandra Weaver in New York City, the daughter of Elizabeth Inglis (née Desiree Mary Lucy Hawkins) (d. 2007), an English former actress, and the NBC television executive Sylvester "Pat" Laflin Weaver (d. 2002), an American of Scottish, Ulster Irish and early New England ancestry. Her uncle, Doodles Weaver, was a comedian and actor. She began using the name "Sigourney Weaver" in 1963, aged fourteen, after a minor character (Sigourney Howard) in F. Scott Fitzgerald's novel The Great Gatsby.

Weaver attended the Ethel Walker School, a prep school in Simsbury, Connecticut where she was made fun of all the time for being a "nerd" and for her height. She also attended The Chapin School She was reportedly 5'10" by age 13, but only grew another inch to her adult height of 5'11". She graduated from Stanford University (BA, English, 1972). She earned an MFA (1974) at Yale School of Drama, where she appeared in the chorus of a production of Stephen Sondheim's The Frogs and as one of a mob of Roman soldiers in another production as well as, later, in original plays by friend and classmate Christopher Durang. She later appeared in the 1981 Off Broadway production of his comedy Beyond Therapy directed by then up-and-coming director Jerry Zaks. She is fluent in French and in German.