The film is based on "mostly true, wildly contradictory" actual interviews from the people represented in the film.
It starts with overlapping faux interviews from Tonya Harding (Margot Robbie), her ex-husband Jeff Gillooly (Sebastian Stan), her mother LaVona (Allison Janney), Tonya's first coach Diane Rawlinson (Julianne Nicholson), her ex-bodyguard Shawn Eckhardt (Paul Walter Hauser), and Hard Copy reporter Martin Maddox (Bobby Cannavale). All of them discuss how Tonya came to be in the figure skating world and what kind of reputation she earned during and after her career.
As a child, Tonya (here played by Mckenna Grace) is pushed by LaVona to join a figure skating class taught by Diane starting at the age of 4 due to Tonya's obsession with it. Although Diane says she doesn't teach beginners, she becomes convinced after seeing Tonya on the ice. However, LaVona is verbally and physically abusive toward her daughter, claiming that this is what pushed Tonya to be as great as she was. Tonya was closer to her father Al (Jason Davis), as he taught her to hunt, but Tonya was devastated when he left her and LaVona.
Tonya meets Jeff at the age of 15. They go on their first date with LaVona accompanying them. They fall in love, but Jeff proves to be just as abusive as LaVona, frequently striking Tonya on a whim. Still, Tonya decides to stay with him in the hopes that things will get better.
In 1986, Tonya competes at Skate America in Portland, ME. She puts on a strong performance but it annoyed that the judges do not present her with her scores.
At home, Tonya has dinner with LaVona. They argue about Jeff, which leads to a physical confrontation that ends with LaVona throwing a knife into Tonya's arm, leaving them both stunned and silent.
Jeff helps Tonya make her own outfit for her next competition, and she knows it's not nearly as flashy as the outfits the other skaters wear. During her next competition, Tonya once again becomes angry that the judges won't present her scores. She confronts the judges in front of the audience, to which one of the judges coldly tells her she might not be as good as she thinks and that she should pick a different sport. Tonya responds with, "Suck my dick!" She goes to the back where Diane meets her, and Tonya fires her, saying she's moving to another coach.
Tonya and Jeff eventually get married, which she acknowledges to have been a dumb thing she because she was young. LaVona shows up and naturally criticizes Tonya for marrying Jeff.
At the 1991 Nationals in Minneapolis, MN, Tonya steps out with her new coach, Dody Teachman (Bojana Novakovic). A heckler attempts to bring Tonya's spirit down, but Dody encourages her. We then see that LaVona paid the heckler to taunt Tonya to motivate her. Here, Tonya becomes the first American woman to successfully pull off a triple axel, to the astonishment of everyone watching. Tonya says this was the moment she knew she was the best figure skater in the world at one point in time, and it makes her emotional.
Both Tonya and Jeff claim that after the triple, everything changed for them. Jeff became even more abusive, and Tonya would maintain her focus on skating to the point that she leaves Jeff. She chimes in at one point to establish that she and Nancy Kerrigan (Caitlin Carver) were friends and that they would hang out in between competitions.
Tonya reconciles with Jeff, but she feels that her skating got worse after this. She continuously stumbles on the ice, but Tonya perseveres and knows she can do better.
At the 1992 Olympics in Albertville, France, Tonya places 4th behind Nancy after messing up most of her landings, which she blames on her skate blade being replaced poorly after it broke a few days earlier. Flashbacks indicate that her weight gain due to constant drinking was also a factor in her loss.
Tonya and Jeff's relationship gets so bad that Tonya starts to file restraining orders until she finally divorces him. Jeff is left alone and remorseful. He eventually finds Tonya in her new home and pulls out a gun, threatening to shoot either her or himself. She runs out of the house, and Jeff fires a shot that ricochets off his truck and hits Tonya above the eye. Jeff tries to drive her to the hospital, but they are pulled over by a cop, and the cop busts Jeff for carrying guns and open booze bottles, but he never notices the wound on Tonya's face.
Tonya starts working at a restaurant to make ends meet. When she goes outside for a smoke, she is found by Diane. She tells Tonya that the next Olympics will be in two years instead of four. Tonya starts training again under Diane to lose weight and build muscle in order for her to compete.
Tonya later speaks to a skating official and acknowledges that he and the other head honchos don't like her, to which he responds that she just doesn't represent a wholesome image that they want to convey. This leads Tonya to go speak to LaVona at the restaurant where she works, as she believes LaVona cursed her, though she tells Tonya that she made her a winner.
Everyone in the interviews now come to talk about "the incident" (Nancy getting her knee whacked by an assailant). Jeff states that there were many contradictory stories, including people claiming that Tonya herself had attacked Nancy.
It begins in 1993 at the NW Regional Championships in Portland, OR. A cop comes to tell Tonya and Jeff that someone called in a death threat against Tonya, saying she will get "a bullet in the back" if she competes. In retaliation, Jeff goes to Shawn to try and send phony death threats to Tonya's competition to scare them. Shawn recruits two of his pals, Derrick Smith (Anthony Reynolds) and Shane Stant (Ricky Russert), to go out to Massachusetts where Nancy trains to try and scare her. Tonya herself is aware of the death threats scare plan. However, Jeff eventually tries to get Shawn to call off the plan, but Shawn thinks they are too far in to call it off.
Shane finds Nancy in Detroit at the rink and spots her in the hallway. He takes out a retractable baton and whacks her knee before trying to escape with Derrick serving as the getaway driver. The doors are locked, so he bashes his head through the glass to get away. Tonya and Jeff see the news on TV themselves with Nancy injured and crying in agony. Jeff angrily confronts Shawn for going ahead with the assault, where Shawn also admits that he had called in the death threat to Tonya before. Shane is eventually found by police and is arrested.
Later on, Tonya qualifies to go to the Olympics. She and Jeff are found by FBI agents and questioned in regards to the incident. They claim to not know anything or to not have witnessed anything themselves. Jeff questions Shawn over how the authorities know the name Derrick. Although Shawn denies saying anything, flashbacks over the last 24 hours show that Shawn stupidly told a few people about Derrick, Shane, and most of their plan. 48 hours after that, the same agents that questioned Tonya and Jeff go to Shawn's house to question him, and he pins the blame entirely on Jeff. They attempt to set Jeff up in a sting operation to confess, but he never gives anything up.
Tonya continues to compete while Jeff, Shawn, Derrick, and Shane are arrested and brought to trial. The press continues to hound Tonya's home, as well as LaVona's. She goes to visit Tonya with the press right behind her. Although Tonya tries to find support and consolation in her mother, LaVona tries to secretly record a confession from Tonya, which she finds out about and sends LaVona out of the house. With the constant threat of arrest and getting kicked out of competitions looming, Tonya remains firm that she knew nothing about the planned attack, while Jeff and the other guys try to say that she did know something.
Tonya goes to compete at the 1994 Winter Olympics in Lillehammer, Norway. Tonya's skate lace messes up, causing her to cry from the pain. She places eighth, while Nancy places second and wins a silver medal behind Oksana Baiul from the Ukraine who wins the gold.
Tonya officially goes to trial following the Olympics. As a result of her hindering the prosecution, she is sentenced to three years probation, a huge fine, 500 hours community service, a psychological evaluation, and she is banned from the U.S. Figure Skating Association for life. This hurts Tonya the most, and she pleads with the judge to serve jail time instead, but his decision is made up.
Through the interviews, Jeff states that he was sentenced to 18 months in prison but served only eight before being paroled. LaVona mentions that she has lost contact with Tonya, and that she couldn't care less, though it's clear that she feels the opposite. Jeff defends Tonya and says she never would have come up with the death threats, and that he feels responsible for ruining her career.
Tonya later competes as a boxer to maintain some kind of career and to stay in the public eye. We see her competing and fighting brutally against her opponent. She reflects on her skating career and how the American public wants someone to love and hate, and how people always ask her to tell the truth. Tonya ends with stating that this is the story of her life, and "that's the fucking truth."
The final text states that Tonya Harding and LaVona Golden have had no contact in several years. Last Tonya heard, LaVona was living in Washington state behind a porn shop. Jeff Gillooly changed his name to Jeff Stone, and he married a woman named Nancy. The two opened up a hair/tanning salon, and he works as a car salesman, happily married with two children. Tonya quit boxing and worked in landscaping, deck building, and house painting. She is happily married with a son and wants everyone to know she's a good mother.
The credits show footage of the real Tonya Harding figure skating on the ice.