The Guardian is a 1990 American supernatural horror film co-written and directed by William Friedkin, and starring Jenny Seagrove as a mysterious nanny who is hired by new parents, played by Dwier Brown and Carey Lowell, to care for their infant son; the couple soon discover the nanny to be a hamadryad, whose previous clients' children went missing under her care. The film is based on the novel The Nanny, by Dan Greenburg.

Director Sam Raimi was originally attached to the project, before dropping out to direct Darkman. Heavily marketed as director Friedkin's first foray into the horror genre since 1973's The Exorcist, the film had a troubled production, with the script undergoing changes that continued well into the shooting process.

The film was released in the spring of 1990, and had a generally unfavorable critical reception, later making Roger Ebert's "most hated films" list. A cable television version of the film was credited to "Alan Von Smithee", due to Friedkin's wish to disassociate himself from its release.