Mollie O'Callaghan

O'Callaghan swam for the Australian team in the preliminaries of all three women's relays at the 2020 Summer Olympics in Tokyo, receiving two gold medals and one bronze for her contribution. Swimming the 1st leg for Australia in the heats of the 4×100 m freestyle relay, she posted a time of 53.08 and received a gold medal after the Australian team won the final.^[2]

In the 4×200 m freestyle relay preliminaries, O'Callaghan swam a junior world record of 1:55.11 when swimming the lead off leg. Her time would have placed her fifth in the 200 m freestyle final.^[3] However, because the Australian coaches had previously decided to use four fresh swimmers in the final, O'Callaghan was not selected for the final where Australia finished third.^[4]

In a heat of the 4×100 m medley relay, O'Callaghan again posted a competitive time; her anchor leg split was 52.35, only 0.24 seconds slower than the fastest freestyle split in the final by Cate Campbell.

O'Callaghan competed at the 2022 World Championships in Budapest. Swimming the first leg of the 4×100 m freestyle relay, she split 52.70. Australia won the gold medal in 3:30.95.^[5] In the 200 m freestyle, she won the silver medal in a time of 1:55.22.^[6] She then competed in the 4×200 m freestyle relay, swimming the anchor leg in a time of 1:55.94. Australia finished with the silver medal, recording 7:43.86.^[7] In the 100 m freestyle, O'Callaghan won the gold medal in a time of 52.67.^[8] She then swam the anchor leg of the mixed 4×100 m freestyle relay, splitting 52.03. Australia won the gold medal in a world record time of 3:19.38.^[9] She concluded the championships with a silver medal in the 4×100 m medley relay.^[10]

Weeks later, O'Callaghan competed at the Swimming at the 2022 Commonwealth Games in Birmingham. She won the silver medal in the 200 m freestyle in a time of 1:54.01, which placed her as the sixth-fastest swimmer in the event's history. She finished 0.12 seconds behind the gold medalist.^[11] Later in the session, she swam the third leg of the mixed 4×100 m freestyle relay, where Australia won the gold medal in a games record of 3:21.18.^[12] The following day, she competed in the women's 4×100 m freestyle relay, splitting 52.66 on the third leg. Australia won the gold medal in a time of 3:30.64.^[13] On the third day, O'Callaghan swam the third leg of the 4×200 m freestyle relay, splitting 1:54.80. Australia won the gold medal in a time of 7:39.29, which broke the world record of 7:40.33 set by China in 2021.^[14] O'Callaghan later competed in the 100 m freestyle, recording 52.63 to win her first individual gold of the competition.^[15] On the final day, she competed in two events. The first of which was the 50 m backstroke, where she won the silver in a time of 27.47.^[16] She then anchored the women's 4×100 m medley relay to the gold medal.^[17]

O'Callaghan was selected for the 2022 World Championships (25 m) in Melbourne. Her first event was the 4×100 m freestyle relay, where she led off in a time of 52.11, with Australia recording 3:25.43 to win the gold medal. This was a new world record, surpassing the Netherlands' mark of 3:26.53 from 2014.^[18] O'Callaghan competed in two events on the second day. First was the 100 m backstroke, where she finished in a time of 55.62 to win the silver medal. Later in the night, she swam the second leg of the 4×200 m freestyle relay, recording a split of 1:52.83. Australia won the gold medal in world record time of 7:30.87, surpassing the Netherlands' mark of 7:32.88 from 2014.^[19][20] The following day, O'Callaghan swam in the 4×50 m freestyle relay, recording 24.01 on the third leg. Australia won the silver medal in an overall time of 1:34.23, which was a new Oceanian record.^[21] On day four, O'Callaghan won the bronze medal in the 50 m backstroke in an Oceanian record time of 25.61.^[22] On day five, O'Callaghan swam the first leg of the 4×50 m medley relay, recording 25.49 to break the Oceanian record in the 50 m backstroke again. Australia won the gold medal in 1:42.35 to break the world record by 0.03 seconds.^[23] O'Callaghan's final swim was the 4×100 m medley relay, swimming the backstroke leg in the heats before she was replaced by Kaylee McKeown in the final. Australia went on to win the silver medal.^[24][25]

O'Callaghan was selected for the 2023 World Championships in Fukuoka. Swimming the first leg of the 4×100 m freestyle relay, she split 52.08, becoming the sixth-fastest woman of all time in the 100 m freestyle. Australia won the gold medal in 3:27.96, breaking their previous world record of 3:29.69 from 2021.^[26] O'Callaghan competed in the 200 m freestyle, trailing Ariarne Titmus for the first three laps of the final. O'Callaghan took the lead during the final lap, winning the gold medal by 0.16 seconds. She went 1:52.85, breaking Federica Pellegrini's world record of 1:52.98 from 2009.^[27] O'Callaghan competed in the 4×200 m freestyle relay, splitting 1:53.66 on the first leg. Australia won the gold medal in a world record time of 7:37.50.^[28] O'Callaghan then recorded 52.16 in the 100 m freestyle to defend her world title in the event, becoming the first woman to win both the 100 and 200 m freestyle events at a single world championships.^[29] She once again anchored the mixed 4×100 m freestyle relay to a new world record, with the team recording a time of 3:18.83.^[30] On the final day of competition, O'Callaghan anchored the 4×100 m medley relay to the silver medal.^[31]

O'Callaghan competed at the 2024 Australian Trials in Brisbane. She came second in the 100 m backstroke with a time of 57.88, becoming the fourth-fastest woman in history.^[32] Her next event was the 200 m freestyle, which served as a rematch with Titmus. They were under world record pace for the entirely of the race, separated by no more than 0.25 seconds. Titmus finished first to break the world record in 1:52.23. O'Callaghan recorded 1:52.48 for the second-fastest time in history.^[33] O'Callaghan later won the 100 m freestyle in a time of 52.33.^[34] O'Callaghan later dropped the 100 m backstroke from her Olympic program.^[35]

On the first night of swimming in Paris, O'Callaghan competed in the 4×100m freestyle relay, splitting 52.24 on the first leg. Australia won the gold medal in 3:28.92, which was an Olympic record and the second-fastest time in history. It was Australia's fourth consecutive Olympic gold medal in the event.^[36]

O'Callaghan once again went head-to-head with Titmus in the 200 m freestyle. O'Callaghan trailed the field in the early stages of the race, but took the lead in the final lap to win the gold medal. She recorded an Olympic record time 1:53.27, surpassing Titmus' mark of 1:53.50 from the Tokyo Olympics. This was Australia's first gold-silver finish in any Olympic event since 2004.^[37][38]

Although O'Callaghan went into the 100 m freestyle as the two-time world champion, she finished fourth in the event. The result was considered one of the biggest surprises of the Olympics.^[39]

O'Callaghan swam the first leg of the 4×200 m freestyle relay, splitting 1:53.52 to give Australia the lead. They won the gold medal in 7:38.08, which was a new Olympic record and the second-fastest time in history.^[40][41] O'Callaghan later swam the anchor leg of the mixed 4×100 m medley relay, contributing a split of 52.01. Australia won the bronze medal in an Oceanian record time of 3:38.76.^[42] Her final event was the women's 4×100 m medley, where she swam the anchor leg and won the silver medal.^[43]

After the Olympics, O'Callaghan made the decision to take a hiatus for the rest of the year.^[44]

Due to her hypermobility, O'Callaghan again sustained a dislocated knee injury in January, affecting her training for several months including water-based training.^[45]

O'Callaghan competed at the 2025 World Championships in Singapore. Her first event was the 4×100m freestyle relay. She led off in 52.79 to give Australia the lead, and the team went on to win the gold medal. Notably their American rivals, who were suffering from gastroenteritis, saw their anchor, Gretchen Walsh, withdraw before the final.^[46] In the 200 m freestyle final, O'Callaghan again emphasised the second half of the race, pulling away at the 100 m mark. She won the gold medal in 1:53.48.^[47] The following day, O'Callaghan swam the anchor leg of the 4×200 m freestyle relay. She dove in with a lead of 0.39 seconds, and was matched up against Katie Ledecky. O'Callaghan split 1:53.44 to win the gold medal in 7:39.35. This marked O'Callaghan's third gold medal of the championships and 11th gold medal overall, equalling Ian Thorpe's record for the most world championship gold medals won by an Australian swimmer.^[48][49] O'Callaghan won the silver medal in the 100 m freestyle, finishing 0.12 behind defending world champion Marrit Steenbergen. Her final event was the 4×100 m medley relay, where she swam the anchor leg in 52.23. Australia won the silver medal in an overall time of 3:52.67.^[50]

In October, O'Callaghan competed in the 2025 World Cup. At the Carmel stop, she went 1:50.77 in the short course 200 m freestyle to become the third fastest woman in the event's history.^[51] At the Westmont stop, O'Callaghan went 1:49.77 in the same event. This broke Siobhán Haughey's world record of 1:50.31 from 2021.^[52] At the Toronto stop, O'Callaghan went 1:49.36 to break the world record again.^[53]

As of 12 June 2024^[54]

As of 11 October 2025^[54]

^a split 52.03 (4th leg); with Jack Cartwright (1st leg), Kyle Chalmers (2nd leg), Madison Wilson (3rd leg)
^b split 1:54.80 (3rd leg); with Madison Wilson (1st leg), Kiah Melverton (2nd leg), Ariarne Titmus (4th leg)
^c split 52.08 (1st leg); with Shayna Jack (2nd leg), Meg Harris (3rd leg), Emma McKeon (4th leg)
^d split 1:53.66 (1st leg); with Shayna Jack (2nd leg), Brianna Throssell (3rd leg), Ariarne Titmus (4th leg)
^e split 51.71 (4th leg); with Jack Cartwright (1st leg), Kyle Chalmers (2nd leg), Shayna Jack (3rd leg)

^a split 52.19 (1st leg); with Madison Wilson (2nd leg), Meg Harris (3rd leg), Emma McKeon (4th leg)
^b split 1:52.83 (2nd leg), with Madison Wilson (1st leg), Leah Neale (3rd leg), Lani Pallister (4th leg)
^c split 25.49 (backstroke leg); with Chelsea Hodges (breaststroke leg), Emma McKeon (butterfly leg), Madison Wilson (freestyle leg)

^a split 52.24 (1st leg); with Shayna Jack (2nd leg), Emma McKeon (3rd leg), Meg Harris (4th leg)
^b split 1:53.52 (1st leg) with Lani Pallister (2nd leg), Brianna Throssell (3rd leg), Ariarne Titmus (4th leg)

• In the 2022 Australia Day Honours, O'Callaghan was awarded the Medal of the Order of Australia.^[56]
• Swimming Australia, Olympic Program Swimmer of the Year: 2022^[57] and 2023^[58]
• Australian Institute of Sport Performance Awards Performance of the Year 2023^[59]

• List of Olympic medalists in swimming (women)
• List of multiple Olympic gold medalists at a single Games
• List of junior world records in swimming