Richardson rose to fame in 2019 as a freshman at Louisiana State University, running 10.75 seconds to break the 100 m collegiate record at the NCAA Division I Championships.

[11] On June 22, 2024, Richardson defended her title as the US national champion in the 100-metre sprint event by winning the women's 100m final in 10.71 seconds (WL),[12] qualifying for the 2024 Summer Olympics in Paris, France, where she won the silver medal in the 100m[13] and gold in the 4×100 relay.

[17][18] She made her international debut at the 2017 Pan American U20 Athletics Championships, where she won a gold medal in the 4 × 100 meter relay alongside Gabriele Cunningham, Rebekah Smith, and Tara Davis.

[19] In 2018, Richardson enrolled at Louisiana State University and began competing for the LSU Lady Tigers track and field team.

[17] At the 2019 NCAA Division I Outdoor Championships, the 19-year-old completed the second-best female one-day double in history after Merlene Ottey, breaking two world U20 records.

[25] A urine sample that she submitted tested positive for THC metabolites indicating recent cannabis use, which put her participation in the Olympics in doubt.

[26][27] After successfully completing a counseling program, she accepted a one-month suspension by the United States Anti-Doping Agency (USADA) that began on June 28, 2021.

[8] While Richardson was ineligible for the Olympic 100 meters due to the suspension ending on July 27, 2021, she could have been eligible for the Women's 4 × 100 relay scheduled for August 5, 2021.

[33] In response to the controversy, in September 2021, the World Anti-Doping Agency announced that it would conduct a review regarding the prohibited status of cannabis.

[34] Cannabis has remained a prohibited drug for Olympic athletes since 1999, though in 2013 the World Anti-Doping Agency increased the level of THC metabolite allowed from 15 ng/mL to 150 ng/mL.

[36] On April 8, 2023, she ran the fourth-fastest 100 m by a woman in all conditions, clocking 10.57 seconds with a strong, illegal 4.1 m/s tailwind to win the women's final at the Miramar Invitational.

On July 7, 2023, Richardson became the US national champion in the 100-metre sprint event by winning the women's 100m final in 10.82 seconds, qualifying for the 2023 World Athletics Championships in Budapest.

[43] At the Olympics 100m Richardson finished second behind Saint Lucia's Julien Alfred, who had a faster start out of the blocks and never relinquished her lead.

[47] Richardson is noted for her long nails and colorful hair on the field, and she has stated that her style is inspired by that of Florence Griffith Joyner.