|National team||United States|
|Born||May 30, 1995|
Lubbock, Texas, U.S.
|Height||5 ft 10 in (177.8 cm)|
|College team||University of Texas|
She won bronze in the 400-meter individual medley at the 2016 Short Course World Championships. She had originally finished 4th, but was elevated to bronze, along with teammate Ella Eastin being elevated to silver, when Ánh Viên Nguyễn was disqualified from second place.
Cox qualified to swim the 200-meter individual medley at the World Championships after finishing second at the 2017 US Nationals. She went on to win the bronze medal in Budapest with a time of 2:09.71. She also won a gold medal as a prelim swimmer of the 4x200 freestyle relay.
Cox was banned from competition for six months after a urine sample taken in February 2018 tested positive for trimetazidine. FINA initially reduced her suspension from four years to two years because of Cox's testimony that she did not knowingly ingest the performance-enhancing drug, but would not reduce it further without evidence of the source of the trimetazidine. Upon analysis of both opened and sealed bottles of Cooper Complete Elite Athletic multivitamins, the Court of Arbitration for Sport determined that the multivitamins were the source, and reduced Cox's suspension to six months. The suspension expired on September 3, 2018. However, as United States Swimming World Championship trials occurred during her suspension, Cox was not able to qualify for the 2019 World Aquatics Championships.
At the 2021 U.S. Olympic Swimming Trials, Cox finished third in the 200 meter individual medley, touching in 2:09.34, missing second place by 0.02 seconds. Her lifetime best time of 2:08.51, swum at the 2021 Longhorn Invite just one month before Olympic Trials, would have qualified her for the Olympic Team. Cox previously announced that she would be retiring from the sport following the 2021 season, in order to begin medical school at the McGovern Medical School, part of the University of Texas Health Science Center at Houston. She subsequently announced her retirement on social media at the conclusion of the meet.
- Pirtle, Krista (July 2, 2015). "The long way: Lubbock native Madisyn Cox swimming for USA in Korea | Lubbock Online | Lubbock Avalanche-Journal". Lubbock Online. Retrieved December 8, 2016.
- Alyssa Goard. "Lubbock Native Madisyn Cox Competing in Olympic Swim Trials". Everythinglubbock.com. Retrieved December 8, 2016.
- "Texas Invitational: Madisyn Cox, Longhorns Clock 3 More Records - Swimming World News". Swimmingworldmagazine.com. Retrieved December 8, 2016.
- "Women's swimming and diving team has a hunger for excellence | The Daily Texan". Dailytexanonline.com. Retrieved December 8, 2016.
- "Madisyn Cox earns bronze at FINA Short Course Championships". Hookem.com. Retrieved December 8, 2016.
- "2016 Short Course Worlds: Team USA Leads Day 1 Medal Table". Swimswam.com. Retrieved December 8, 2016.
- "Vietnamese swimming star's DQ erases historic finish - CBC Sports - Aquatics". Cbc.ca. Retrieved December 8, 2016.
- "FINA reduces doping ban for world champ Madisyn Cox". CBC. September 3, 2018. Retrieved September 3, 2018.
- Gibbs, Robert (August 31, 2018). "Madisyn Cox's Suspension Reduced to Six Months after Trimetazidine Detected in Multivitamin". SwimSwam. Retrieved September 3, 2018.
- "Madisyn Cox Eligible to Compete After Source For Banned Substance Found in Multivitamin". Swimming World News. August 31, 2018. Retrieved September 3, 2018.
- "Madisyn Cox Swims Fastest 200 IM of 2021 at Longhorn Invite Day 3 Finals". SwimSwam. May 23, 2021. Retrieved June 22, 2021.