
Margaret JoBeth Williams (born December 6, 1948) is an Academy Award, Golden Globe, and Emmy nominated American film and television actress and director, and current President of the Screen Actors Guild Foundation.
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 (1994).
Her directorial debut with the 1994 short film On Hope earned her an Academy Award nomination for Best Live Action Short Film.
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).
In 2009 she began serving as president of the Screen Actors Guild Foundation; she is President Emeritus of the foundation.
She has also had numerous guest starring roles on TV and has starred in several TV movies.

Poltergeist
1982 · as Diane Freeling

Wyatt Earp
1994 · as Bessie Earp

Stop! Or My Mom Will Shoot
1992 · as Lt. Gwen Harper

Kramer vs. Kramer
1979 · as Phyllis Bernard

The Day After
1983 · as Nurse Nancy Bauer

Switch
1991 · as Margo Brofman

The Big Chill
1983 · as Karen Bowens

The Big Year
2011 · as Edith

Stir Crazy
1980 · as Meredith

Poltergeist II: The Other Side
1986 · as Diane Freeling

The Dogs of War
1980 · as Jessie

Fever Pitch
2005 · as Maureen Meeks

Jungle 2 Jungle
1997 · as Dr. Patricia Cromwell

Not Without Hope
2025 · as Marcia

In the Land of Women
2007 · as Agnes Webb

Endangered Species
1982 · as Harriet Purdue

Memories of Me
1988 · as Lisa

Uncorked
2009 · as Sophia Browning