Marcia Gay Harden (born August 14, 1959) is an American actress. She is the recipient of various accolades, including an Academy Award and a Tony Award, in addition to nominations for three Primetime Emmy Awards.

Born in the La Jolla area of San Diego, California, Harden began her acting career appearing in television programs throughout the 1980s. In 1986, she appeared in her first film role, with her breakthrough coming in the 1990 Coen brothers–directed Miller's Crossing. For her portrayal of artist Lee Krasner in the 2000 biographical film Pollock, she won the Academy Award for Best Supporting Actress. She received a second Academy Award nomination for her performance as Celeste Boyle in the drama film Mystic River (2003). Her other notable film credits include The First Wives Club (1996), Flubber (1997), Space Cowboys (2000), Mona Lisa Smile (2003), and the Fifty Shades film trilogy.

Harden made her Broadway debut in 1993, starring in Tony Kushner's epic play Angels in America: Millennium Approaches/Angels in America: Perestroika for which she was nominated for a Tony Award for Best Featured Actress in a Play. She returned to Broadway in 2009 as Veronica in Yazmina Reza's comedic play God of Carnage, with her performance earning her the Tony Award for Best Actress in a Play.

Harden's television credits include the HBO series The Newsroom, the ABC series How to Get Away with Murder, the Apple TV+ series The Morning Show, and CBS series Code Black and So Help Me Todd. She received her first Primetime Emmy Award nomination for her role as FBI Special Agent Dana Lewis in the crime drama series Law & Order: Special Victims Unit, and earned a second Primetime Emmy Award nomination for her performance as Janina Krzyżanowska in the television film The Courageous Heart of Irena Sendler (2009).