David Popovici KSR (Romanian pronunciation: [ˈdavid po'povit͡ʃʲ]; born 15 September 2004) is a Romanian competitive swimmer who specializes in freestyle events and is the reigning Olympic champion in the 200-metre event, having won the gold medal at the 2024 Summer Olympics. He is the current holder of the European record and the junior world record, as well as the former holder of the world record in the long course 100-metre freestyle. He is also the holder of the current junior world record in the short course 100-metre freestyle event and in the long course 200-metre freestyle event.

At the 2022 World Aquatics Championships, Popovici won gold medals in his two signature events (Men's 100-metre freestyle and Men's 200-metre freestyle), becoming the first swimmer to do so at the same edition of the World Championships, since Jim Montgomery in 1973. Following his performances during the 2022 long course season, in which he won eleven gold medals and two silver medals, Popovici was voted Male Swimmer of the Year by both SwimSwam and Swimming World Magazine. He was also named the BTA Best Balkan Athlete of the Year of 2022. During that summer, he established an unprecedented level of dominance, especially in the long course 100-metre freestyle, recording 13 of the 19-fastest swims in the world in 2022, while also becoming only the third swimmer in history to set an under 1:43 time in the long course 200-metre freestyle. At the 2024 Paris Olympics, he placed third in the 100-metre freestyle, earning the bronze medal, finishing just 0.01 seconds behind Australia's Kyle Chalmers.

Popovici was born in Bucharest, Romania, and he started swimming at Lia Manoliu pool at the age of 4, at a doctor's recommendation to correct early stage scoliosis. At the age of 9 he began to train at Aqua Team Bucharest, under coach Adrian Rădulescu, a former swimmer with a PhD in athletic performance specialized in swimming. At the age of 10, Popovici broke his first junior national record, in 50 m backstroke – a 24-year-old record held by Dragoș Coman, a 2003 world bronze medalist. At 14 he became the fastest swimmer under 15 in the history of the European Youth Olympic Festival, swimming 100 meters in 49.82 seconds.

At the 2020 European Aquatics Championships in Budapest, which took place from 10 to 23 May 2021 due to the COVID-19 pandemic, Popovici managed to swim below the Olympic Qualifying Time in the Men's 100-metre freestyle event and by doing so, he qualified for the Tokyo 2020 Olympics, being the youngest member of the Romanian team. He broke the Romanian national record three times during the event (in the heats, semifinal and final), finishing sixth place in the final. Popovici also competed in the Men's 50-metre freestyle and the Men's 200-metre freestyle, meeting the Olympic Selection Time in both of the events.

Popovici won a total of four medals, at the 2021 European Junior Swimming Championships in Rome, where he broke the 100-metre freestyle junior world record twice. In the 4x100-metre freestyle relay, he broke the junior world record for the first time, with a time of 47.56, helping the relay win the silver medal. Two days later, he managed to break the same junior world record again, this time in the 100-metre freestyle event, to win the gold medal, with a time of 47.30. This performance made Popovici the fastest man in the world at that time in 2021, surpassing Kliment Kolesnikov. His second gold medal of the European Junior Championships came in the 200-metre freestyle event, where he broke another junior world record in the semifinal, with a time of 1:45.26. He won his third gold medal in the 50-metre freestyle event, where he finished 0.61 seconds ahead of second-place finisher Nikita Chernousov.

At the 2020 Summer Olympics in Tokyo, which were postponed to 2021 due to the COVID-19 pandemic, Popovici competed in the 50-metre, 100-metre, and 200-metre freestyle individual events, following his good performances at the European Championships. While he did not win a medal, he was only 0.02 seconds behind bronze medalist Fernando Scheffer, and ahead of Martin Malyutin (who won the gold medal at the European Championships), as he finished fourth in the Men's 200-metre freestyle, with a time of 1:44.68. In the Men's 100-metre freestyle, Popovici once again asserted himself as a medal contender, qualifying for the final (47.72) and ultimately placing seventh, with a time of 48.04.

To follow-up a pair of national records accomplished while racing at the FINA World Cup meet in Kazan, clocking respective performances of 46.77 in the 100-metre freestyle, and 1:43.58 in the 200-metre freestyle, Popovici entered to compete at the 2021 European Short Course Swimming Championships held at the Kazan Aquatics Palace in Russia. On 6 November, Popovici won the gold medal in the Men's 200-metre freestyle event, with a time of 1:42.12, breaking his own national record from the World Cup. He failed to qualify for the finals in the Men's 100-metre freestyle, and Men's 400-metre freestyle individual events.

In his first of two events at the 2021 World Short Course Championships, the 400-metre freestyle on 16 December, Popovici placed thirty-second with a time of 3:46.08 and did not qualify for the evening final. For his second event, the 200-metre freestyle the following day, he ranked fourteenth in the preliminary heats with a 1:43.62, not qualifying for the final of the event.