Plot
Two 28-year-old women, Romy White and Michele Weinberger, live together in an apartment in Venice, Los Angeles, California. Romy works as a cashier in the service department at a Jaguar dealership and Michele is unemployed. They are single, unambitious, and enjoy a casual lifestyle of slacking, mocking TV and movies, and elaborate amateur dressmaking. While working, Romy encounters her former classmate from high school, Heather Mooney. Once a rebellious, troubled girl who frequently smoked cigarettes in school, she is now a businesswoman who invented the paper for a fast-burning cigarette. Heather informs Romy about their upcoming ten-year high school reunion in Tucson, Arizona.
As high school students in 1987, Romy and Michele were continually bullied by the "A-Group," a small group of popular, yet mean, girls, led by cheerleader Christie Masters, who humiliated them repeatedly. Romy also had a crush on Christie’s boyfriend, athlete Billy Christianson. Heather was in love with a geek named Sandy Frink, but Sandy had a crush on Michele. Heather often blew off steam by bullying a girl called Toby Walters. Finally, at the prom, Romy asked Billy if he would dance with her. Though he agreed, when he spoke to Christie about it, she decided to take advantage of the situation. Christie tricked Romy and Michele into thinking Billy was in love with Romy, and had dumped Christie to be with her. Romy waited all night to dance with Billy, who had already left with Christie. Michele danced with her instead.
Romy realizes that their lack of achievements will not make a good impression at the reunion. Desperate to impress their former classmates, Romy and Michele make last-ditch attempts to improve themselves, to no avail. In the end, they decide to fake success by showing up in an expensive car and business suits. Romy borrows a Jaguar XJ-S from a co-worker, and Michele makes their outfits. En route to the reunion, they decide to claim that they invented the Post-it note, believing that no one will know better. They confront over the details of their lie, which escalates into an argument about their friendship. They decide to go their separate ways once they reach the reunion.
At the reunion, Michele hears Romy claiming that she invented Post-its by herself. Michele convinces the A-Group she invented a special kind of glue. Sandy Frink, the nerd who had a crush on Michele in high school, has become wealthy and attractive since high school, and hits on Michele after hitting her with his limo. Billy and Romy reunite and hit it off. Both Romy and Michele win awards as the "Most Changed For the Better Since High School" members of their graduating class, but still refuse to speak with each other. Seventy years later, an elderly Michele learns that Romy is on her deathbed, and calls her to make amends. However, they rehash the same argument and Romy dies without resolving their issues.
Michele wakes up alone in the Jaguar, realizing that she was dreaming. At the reunion, Romy starts to tell the Post-it story to the A-group, who are all pregnant. Christie Masters is now a mother of two children, with a third on the way, and married to Billy, who, according to Christie, works in real estate. Heather arrives (hoping to seduce Sandy Frink) and Christie mentions Romy’s Post-it story, but Heather reveals the lie by telling everyone the real inventor's name. Christie and her friends taunt Romy, and Michele ineptly defends her. Romy runs out, and Michele chases after her. They reconcile and decide to be themselves instead of trying to impress other people. They change into brightly colored homemade outfits and return to the reunion.
They confront Christie, who makes fun of their clothes. A-Group girl Lisa Luder, who lost touch with the A-group after high school and has changed for the better, is now a fashion editor for Vogue, and announces that the outfits are actually "not bad." Christie verbally attacks Lisa, who coolly dismisses and mocks her. The other A-Group women abandon Christie, while everyone else congratulates Romy and Michele. Heather apologizes to Romy and Michele for ruining their story, and admits she was miserable in high school because Sandy was in love with Michele, and didn’t even want to be friends with her. She also mentions that she had no idea Romy and Michele were so badly bullied by the A-group, thinking their lives were perfect. Romy and Michele comfort her by reminding her that she was always successful at making Toby Walters miserable. Just at that moment, Toby asks Heather if she will sign her yearbook as she never did in high school. After Toby admits that Heather always hurt her feelings when they were teenagers, Heather is amazed and happily agrees to sign Toby’s yearbook.
Sandy, now wealthy and successful, arrives via helicopter. He confesses that he still loves Michele and asks her to dance with him. Michele agrees, as long as Romy can dance with them. After their interpretive dance to Cyndi Lauper's "Time After Time", they receive huge applause, and Sandy escorts them to his helicopter. On their way out, they encounter Billy. Once a muscular and handsome athlete, he is now an overweight alcoholic, has a dead-end job installing drywall for Christie's father, and is unsure if he is the father of her latest pregnancy. He hits on Romy, who tells him to wait for her in his hotel room. As revenge for making her feel so insecure because of the prom trick, she plans to do the exact same thing to him. She then leaves the reunion with Michele as the two girls join Sandy in his helicopter. The reunion guests watch as the helicopter takes off.
Six months later, back in Los Angeles, Romy and Michele have opened a successful fashion boutique with their homemade designs using money borrowed from Sandy.
