Linda Denise Blair (born January 22, 1959) is an American actress and activist. She is known for portraying Regan MacNeil in the horror film The Exorcist (1973), which won her a Golden Globe and a nomination for the Academy Award for Best Supporting Actress. The film established her both as a scream queen and in popular culture. She reprised the role in two sequels: Exorcist II: The Heretic (1977) and The Exorcist: Believer (2023).

Blair has starred in several television films, including Born Innocent (1974), Sarah T. – Portrait of a Teenage Alcoholic (1975), and Stranger in Our House (1978). She has also starred in exploitation and grindhouse films, including Hell Night (1981), Chained Heat (1983), and Savage Streets (1984). Her role in the musical film Roller Boogie (1979) brought her renewed recognition as a sex symbol. She was the host of the Fox Family reality series Scariest Places on Earth (2000–2006) and made appearances on the Animal Planet series Pit Boss (2010–2012).

Blair is a prominent activist for the animal rights movement. In 2004, she founded the Linda Blair WorldHeart Foundation, a non-profit organization that works to rehabilitate and adopt rescue animals.

Linda Denise Blair was born on January 22, 1959, in St. Louis, Missouri, to James Frederick and Elinore (née Leitch) Blair. Blair is of Scottish ancestry. She has an older sister, Debbie, and an older brother, Jim. When Linda was two years old, her father, a Navy test pilot-turned-executive recruiter, took a job in New York City, and the family relocated to Westport, Connecticut. Her mother worked as a real-estate agent in Westport. Linda worked as a child model at age five, appearing in Sears, JCPenney and Macy's catalogues, and in over 70 commercials for Welch's grape jams and various other companies. She secured a contract at age six for a series of print advertisements in The New York Times. At the same age, she began riding horses, later becoming a trained equestrian.

Blair started acting with a regular role on the short-lived Hidden Faces (1968–69) daytime soap opera. Her first theatrical film appearance was in The Way We Live Now (1970), followed by a bit part in the comedy The Sporting Club (1971). In 1972, She was selected from a field of 600 applicants for her most notable role as Regan, the possessed daughter of a famous actress, in William Friedkin's The Exorcist (1973). The role earned her a Golden Globe for Best Supporting Actress, and an Academy Award nomination for Best Supporting Actress. Film critic and historian Mark Clark notes that in her performance, "Blair matches [adult co-star] Ellen Burstyn note-for-note." Despite the film's critical successes, Blair received media scrutiny for her role in the film, which was deemed by some as "blasphemous", and she has said the film had significant impact on her life and career. After the film's premiere in December 1973, some reporters speculated about Blair's mental state, suggesting the filming process had resulted in her having a mental breakdown, which she denied, and she later received anonymous death threats. To combat the rumors and news media speculation surrounding her, Warner Bros. sent the then-14-year-old Blair on an international press tour in hopes of demonstrating that she was "just a normal teenager".

Blair starred opposite Kim Hunter in the controversial television film Born Innocent (1974), in which she plays a runaway teenager who is sexually abused. The film was criticized by the National Organization for Women, the New York Rape Coalition, and numerous gay and lesbian rights organizations for its depiction of female-on-female sexual abuse; the Lesbian Feminist Liberation dismissed the film, stating: "Men rape, women don't," and regarded the film as "propaganda against lesbians." After filming Born Innocent, Blair also had a supporting part as a teenaged kidney-transplant patient in the disaster film Airport 1975 (1974), which was critically panned, but a success at the box office. A steady series of job offers led her to relocate to Los Angeles in 1975, where she lived with her older sister, Debbie. Between 1975 and 1978, she had lead roles in numerous television films: Sarah T. – Portrait of a Teenage Alcoholic (1975), as a teenager who becomes addicted to alcohol; Sweet Hostage (1975) opposite Martin Sheen, in which she plays a kidnapping victim; and Victory at Entebbe (1976), a dramatization of a real-life hostage situation starring Anthony Hopkins and Elizabeth Taylor.

In 1977, Blair reprised her role as Regan in the Exorcist sequel, Exorcist II: The Heretic (1977), garnering a Saturn Award nomination for Best Actress of 1978. The film was a critical and commercial failure, however, and at the time was the most expensive film ever made by Warner Bros. Studios. After filming Exorcist II: The Heretic, she took a year off from acting and competed in national equestrian circuits under the pseudonym Martha McDonald. In 1978, she made a return to acting in the Wes Craven-directed television horror film Stranger in Our House (retitled Summer of Fear), based on the novel by Lois Duncan, and also with the lead role in the Canadian production Wild Horse Hank, in which she used her equestrian skills to play a college student saving wild horses from ranchers.

Blair's career took a new turn in 1979 with her starring role in the musical drama Roller Boogie, which established her as a sex symbol. The following year, she co-starred with Dirk Benedict in Ruckus, playing a young woman who helps a maligned Vietnam veteran evade antagonistic locals in a small town. She also starred in a number of financially successful low-budget horror and exploitation films throughout much of the 1980s. She starred opposite Peter Barton and Vincent Van Patten in the slasher film Hell Night (1981), followed by roles in the women-in-prison film Chained Heat (1983), playing a teenager in a women's prison, and the exploitation thriller Savage Streets (1984), in which she played the leader of a female vigilante street gang who target male rapists. In a review of Savage Streets published by TV Guide, her performance was deemed "her best since The Exorcist (1973)... and that's not saying much." Also in 1983, Blair posed nude in an issue of Playboy. In 1985, she starred again in another women-in-prison feature titled Red Heat, playing a prisoner of war in West Germany. This was followed by a lead in the direct-to-video film Night Force (1985), in which she portrayed a woman who travels to Mexico to save her friend from terrorists.