Margaret JoBeth Williams (born 6 December 1948) is an American film, television, and stage actress.
Williams rose to prominence appearing in such films as Stir Crazy (1980), Poltergeist (1982), The Big Chill (1983), The Day After (1983), Teachers (1984), and Poltergeist II: The Other Side (1986). A three-time Emmy Award nominee, she was nominated for Outstanding Lead Actress in a Miniseries or a Movie for her work in the TV movie Adam (1983) and the TV miniseries Baby M (1988). Her third nomination was for her guest role in the sitcom Frasier (1993–94). She also starred in the TV series The Client (1995–96) and Private Practice (2009–11).
Her directorial debut with the 1994 short film On Hope earned her an Academy Award nomination for Best Live Action Short Film.
Williams was born in Houston, Texas, and attended Jones High School, from which she graduated in 1966. In 1970, she graduated from Pembroke College in Brown University in Providence, Rhode Island, intending to become a child psychologist. Instead, she turned to theater. She trained at the Trinity Repertory Company, taking voice lessons to neutralize her Texan accent. Then she moved to New York City and began to appear in television series in the mid-1970s.
- Since 2009, she has served as president of the Screen Actors Guild Foundation.