When Billie Jean King (Emma Stone) becomes the number-one women's tennis player in the world, she questions why male tennis players are making more than 10 times what she earns. She doesn't get a reasonable answer, so along with other top female tennis players, she and her manager (Sarah Silverman) refuse to participate in any of the tournaments that have been organized that don't offer equal pay, and form their own tour.
Meanwhile, former tennis champ Bobby Riggs (Steve Carell) is living a great post-tennis life with his wealthy wife (Elisabeth Shue), but he misses the thrills of the sport. Calling himself a male chauvinist, he challenges Billie Jean to a match that has a $35,000 purse attached to it. Billie Jean turns it down, believing it to be nothing more than a ridiculous stunt. However, Riggs doesn't give up, going to great lengths to get Billie Jean to play him in a "Battle of the Sexes."