The Philadelphia Story is a 1940 American romantic comedy film starring Cary Grant, Katharine Hepburn, James Stewart and Ruth Hussey. Directed by George Cukor, the film is based on the 1939 Broadway play of the same name by Philip Barry about a socialite whose wedding plans are complicated by the simultaneous arrival of her ex-husband and a tabloid magazine journalist. The socialite, played by Hepburn in both productions, was inspired by Helen Hope Montgomery Scott (1904–1995), a Philadelphia heiress who had married Barry's friend.

Written for the screen by Donald Ogden Stewart and an uncredited Waldo Salt, it is considered among the best examples of a comedy of remarriage, in which a couple divorce, flirt with outsiders and then remarry. The genre was popular in the 1930s and 1940s at a time when divorce was considered scandalous and the depiction of extramarital affairs was blocked by the Production Code.

The film was Hepburn's first hit following several flops that caused her placement on a 1938 list of actors considered to be "box office poison" compiled by theater owner Harry Brandt. Hepburn starred in the play and acquired the film rights, with the help of Howard Hughes, to control it as a vehicle for her screen comeback.

Nominated for six Academy Awards, including Outstanding Production (Best Picture), the film won two: Best Actor (Stewart) and Best Adapted Screenplay. MGM remade the film in 1956 as a musical retitled High Society, starring Bing Crosby, Grace Kelly and Frank Sinatra.

The Philadelphia Story was produced by Joseph L. Mankiewicz and was selected for preservation in the United States National Film Registry in 1995.