Mary Gaitskill (born November 11, 1954) is an American novelist, essayist, and short story writer. Her work has appeared in The New Yorker, Harper's Magazine, Esquire, The Best American Short Stories (1993, 2006, 2012, 2020), and The O. Henry Prize Stories (1998, 2008). Her books include the short story collection Bad Behavior (1988) and Veronica (2005), which was nominated for both the National Book Award for Fiction and the National Book Critics Circle Award for Fiction.

Gaitskill was born in Lexington, Kentucky. She has lived in New York City, Toronto, San Francisco, Marin County and Pennsylvania, and attended the University of Michigan, where she earned her B.A. in 1981 and won a Hopwood Award. She sold flowers in San Francisco as a teenage runaway. In a conversation with novelist and short-story writer Matthew Sharpe for BOMB Magazine, Gaitskill said she chose to become a writer at age 18 because she was "indignant about things—it was the typical teenage sense of 'things are wrong in the world and I must say something.'" Gaitskill has also recounted (in her essay "Revelation") becoming a born-again Christian at age 21 but lapsing after six months.

She married writer Peter Trachtenberg in 2001; they divorced in 2010.

Gaitskill has taught at UC Berkeley, the University of Houston, New York University, The New School, Brown University, Syracuse University, and in the MFA program at Temple University. She has previously been a Writer-In-Residence at Hobart and William Smith Colleges and Baruch College. As of 2020, Gaitskill is a visiting professor of literature at Claremont McKenna College.

Gaitskill attempted to find a publisher for four years before her first book, the short story collection Bad Behavior, was published in 1988. The first four stories are written in the third person point of view primarily from the perspectives of male characters (the second story "A Romantic Weekend," is split between one male and one female character's point of view). The remaining five stories are written from the perspectives of female characters. 'Secretary' is the only story in the book written in the first-person point of view. Several of the stories have themes of sexuality, romance, love, sex work, sadomasochism, drug addiction, being a writer in New York City, and living in New York City. 'A Romantic Weekend' and 'Secretary' both explore themes of BDSM and psychological aspects of dominance and submission in sexual relationships. The story 'Connection' is about the growth and breakdown of a female friendship.

Gaitskill's fiction is typically about female characters dealing with their own inner conflicts, and her subject matter matter-of-factly includes many "taboo" subjects such as prostitution, addiction, and sado-masochism. Gaitskill says that she had worked as a stripper and call girl. She showed similar candor in an essay about being raped, "On Not Being a Victim," for Harper's Magazine.

Gaitskill's 1994 essay in Harper's Magazine also addresses feminist debates about date rape, victimization, and responsibility. She describes ways that individual subjectivity influences all experiences, making it impossible to come to "universally agreed-upon conclusions."

The film Secretary (2002) is based on the short story of the same name in Bad Behavior, although the two have little in common. She characterized the film as "the Pretty Woman version, heavy on the charm (and a little too nice)," but observed that the "bottom line is that if [a film adaptation is] made you get some money and exposure, and people can make up their minds from there."