Margaret JoBeth Williams (born December 6, 1948) is an American actress. She 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 (1994). She also starred in the TV series The Client (1995–96) and had recurring roles in the TV series Dexter (2007) 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. In 2009, she began serving as president of the Screen Actors Guild Foundation; she is President Emeritus of the foundation.

Early life
Williams was born in Houston, Texas, and is the daughter of Frances Faye (née Adams), a dietitian, and Fredric Roger Williams, an opera singer and manager of a wire and cable company. Williams grew up in the South Park neighborhood of Houston, and attended Jones High School, from which she graduated in 1966.