Jennifer Jason Leigh (born Jennifer Leigh Morrow; February 5, 1962) is an American actress. She began her career on television during the 1970s before making her film breakthrough in the teen film Fast Times at Ridgemont High (1982). She received critical praise for her performances in Last Exit to Brooklyn (1989), Miami Blues (1990), Backdraft (1991), Single White Female (1992), and The Hudsucker Proxy (1994), and was nominated for a Golden Globe Award for her portrayal of Dorothy Parker in Mrs. Parker and the Vicious Circle (1994). For her role as fugitive Daisy Domergue in The Hateful Eight (2015), she was nominated for the Golden Globe and an Academy Award for Best Supporting Actress.

Leigh starred in a 1995 film written by her mother, screenwriter Barbara Turner, titled Georgia. She co-wrote and co-directed a film with Alan Cumming titled The Anniversary Party (2001). Leigh starred in the crime drama Road to Perdition (2002) and the family drama Margot at the Wedding (2007). She had a recurring role on the Showtime comedy-drama series Weeds (2009–2012) and received critical acclaim for her voice work in Charlie Kaufman's Anomalisa (2015). From 2017 to 2021, she starred in the Netflix comedy-drama series Atypical, while featuring in the science fiction films Annihilation (2018) and Possessor (2020). She has since starred in the fifth season of the crime drama series Fargo (2023).

For her stage work, Leigh was nominated for a Drama Desk award for her off-Broadway performance as Beverly Moss in Mike Leigh's Abigail's Party. Her Broadway debut occurred in 1998, when she became the replacement for the role of Sally Bowles in the musical Cabaret.

Leigh was born February 5, 1962, in Los Angeles, California. Her father, Vic Morrow (born Victor Morozoff), was an actor, and her mother, Barbara Turner, was a screenwriter. Her parents divorced when she was two. Leigh's birth name was Jennifer Leigh Morrow. She changed her surname early in her acting career, taking the middle name "Jason" in honor of actor Jason Robards, a family friend. Leigh's parents were Jewish; her father's family was from Russia and her mother's from Austria.

Leigh is the younger of two daughters. Her older sister, Carrie Ann Morrow, who was credited as a "technical advisor" on her 1995 film Georgia, died in 2016. Leigh also has a half-sister, actress Mina Badie (born 'Badiyi' – from her mother's second marriage). Badie acted alongside Leigh in The Anniversary Party. Film director Reza Badiyi became Leigh's stepfather when he married Leigh's mother, Barbara.

Leigh had a nonspeaking role in her film debut Death of a Stranger (The Execution) (1973). At the age of 14, she attended acting workshops, taught by Lee Strasberg, and the Stagedoor Manor Performing Arts Training Center in Loch Sheldrake, New York. Afterwards, she landed a role in the film The Young Runaways (1978). She also appeared in an episode of Baretta and an episode of The Waltons. Several television films followed, including a portrayal of an anorexic teenager in The Best Little Girl in the World, for which Leigh dropped to 86 pounds (39 kg). She made her film debut, as a blind, deaf and mute rape victim in the 1981 slasher film Eyes of a Stranger. She left school to star in the film.

In 1982, Leigh played the role of Stacy Hamilton in Amy Heckerling's high school film Fast Times at Ridgemont High, which served as a launching pad for several of its young stars. While decrying the writing as sexist and exploitative, film critic Roger Ebert was enthusiastic about the acting, singling out Leigh and writing, "Don't they know they have a star on their hands?" With the exception of Ridgemont High and a supporting role in the comedy film Easy Money (1983) alongside Rodney Dangerfield, Leigh's early film work consisted of playing fragile, damaged or neurotic characters in low-budget horror or thriller films. She played a virginal princess kidnapped and raped by mercenaries in Flesh and Blood (1985), an innocent waitress pursued by the psychopathic title character in The Hitcher (1986) (both films pitting her alongside Rutger Hauer), a mentally-disturbed, child-like young woman on the threshold of sexual awakening in the Southern Gothic film Sister, Sister (1987), and a young woman on the verge of a nervous breakdown in Heart of Midnight (1989).

She was selected as one of "America's 10 Most Beautiful Women" by Harper's Bazaar in 1989.