Freaky Friday is a comedic children's novel written by Mary Rodgers, first published by Harper & Row in 1972. The plot is set in a day in the life of 13-year-old Annabel Andrews and her mother, who spend one Friday in each other's bodies.

The novel has been adapted for several films, all by the Walt Disney Company and all with the same title as the book: one in 1976, one in 1995, one in 2003, and one in 2018.

In 2025, Freaky Friday was reissued in commemoration of Freakier Friday, the sequel to the 2003 film adaptation of the novel.

The premise of a parent swapping bodies with a child was earlier used in F. Anstey's 1882 novel Vice Versa.

A willful, disorganized teenage girl, Annabel Andrews, awakens one Friday morning to find herself in the body of her mother, with whom she had argued the previous night.

Annabel suddenly finds herself in charge of the New York family's affairs and must now take care of her younger brother Ben (whom Annabel has not-so-affectionately nicknamed "Ape Face" and described as "so neat, it's revolting!"). She grows increasingly worried about the disappearance of "Annabel," who appeared to be herself in the morning but has gone missing after leaving the Andrews' home, and she enlists the help of her neighbor and childhood friend, Boris, though without telling him about her identity crisis.

As the day wears on and Annabel has a series of increasingly bizarre and frustrating adventures, which includes the sacking of the alcoholic and thieving cleaning woman, she becomes gradually more appreciative of how difficult her mother's life is. She learns, to her surprise, that Ben idolizes her, and Boris is actually named Morris, but has a problem with chronic congestion (at least around Annabel) leading him to nasally pronounce m's and n's as b's and d's. As the novel approaches its climax, Ben also disappears, apparently having gone off with a gorgeous girl whom Boris did not recognize, but Ben appeared to trust without hesitation.

In the climax and dénouement, Annabel becomes overwhelmed by the difficulties of her situation, the apparent disappearance of her mother, the loss of the children, and the question of how her odd situation came about and when/whether it will be resolved. Finally, it is revealed that Annabel's mother herself caused them to switch bodies through some unspecified means, and the mysterious teen beauty who took Ben was Mrs. Andrews in Annabel's body (to which she is restored) made much more attractive by a makeover Mrs. Andrews gave the body while using it, including the removal of Annabel's braces, an appointment Annabel had forgotten about (and would have missed, had she been the one in her body that day).