On the Basis of Sex is a 2018 American biographical legal drama film based on the life and early cases of Ruth Bader Ginsburg, who was the second woman to serve as an Associate Justice of the United States Supreme Court. Directed by Mimi Leder and written by Daniel Stiepleman (Ginsburg's real-life nephew), it stars Felicity Jones as Ginsburg. Armie Hammer, Justin Theroux, Jack Reynor, Cailee Spaeny, Sam Waterston, and Kathy Bates feature in supporting roles.

The film had its world premiere at the AFI Fest on November 8, 2018, and was theatrically released in the United States on December 25, 2018, by Focus Features. On the Basis of Sex received generally favorable reviews from critics, who praised Jones' performance, the film's intricacy and its pacing at a dramatic level. Other critics felt the biopic was predictable, over-packaged and hagiographic. Made on a $20 million budget, On the Basis of Sex grossed $38.8 million at the box office.