Up Your Legs Forever is a 1971 film by John Lennon and Yoko Ono. The film was made on 14 December 1970 on West 61st Street in Manhattan, New York City, though the couple did not have permits to work in the United States at that time.

The film was based on Ono's earlier script Film No. 12 (Up Your Legs Forever). The earlier script was also known as Film No. 12 (Esstacy). The script reads "The camera work of the film should constantly go up, up, up, non-stop. Collect 367 pairs of legs and just go up the legs (from toes to the end of thighs) pair after pair and go on up until you run through the whole 367".

The participants in the film were paid $1 each for their appearance, and each received a black and white instant photograph of them taken by Lennon.

The writer Jonathan Cott in his 2013 book Days That I'll Remember: Spending Time With John Lennon & Yoko Ono wrote that Ono told him that "We can't have peace until we expose ourselves to each other. After you communicate like that then maybe we can have peace. And everyone who's in the film, including you, will be a star".

The film was made for a three evening series of films by Lennon and Ono at New York City's Elgin Theater.

Notable participants in the film included filmmaker Shirley Clarke, each member of the band New York Dolls, writer Paul Krassner, lawyer Allen Klein, artist Peter Max, model Taylor Mead, filmmaker Jonas Mekas, filmmaker D. A. Pennebaker, artist Larry Rivers, artist George Segal, film director Jack Smith and writer Tom Wolfe.