In her time as a junior swimmer, McIntosh broke over 50 Canadian national Age Group Records. In May 2021, McIntosh swam a 4:05.13 in the 400 meter freestyle, the fastest time ever recorded worldwide by a 14-year-old female swimmer.
2021 season As part of the 2021 Canadian Olympic swimming trials in
Toronto, McIntosh won the 200 meter freestyle event over training partner
Penny Oleksiak, with a personal best time of 1:56.19, which also marked the fastest time ever by a 14-year-old swimmer worldwide. This qualified her for the
2020 Summer Olympics in Tokyo. McIntosh followed this up with a win in the 800 meter freestyle event, in another personal best time of 8:29.49. She was the youngest person named to the
Canadian Olympic team.
Summer Olympic Games In her first event, McIntosh finished fourth in the
400 meter freestyle, breaking the Canadian national record with a time of 4:02.42. She advanced to the semifinals of the
women's 200m freestyle, but placed ninth there and thus missed the final. She was part of the Canadian team for the
4 × 200 meter relay, along with Oleksiak,
Rebecca Smith and
Kayla Sanchez. They set a new Canadian record in the event final, placing fourth. McIntosh's last event was the
800 metre freestyle, where she placed eleventh and thus did not advance to the final. Following the Olympics, McIntosh made her debut in the
International Swimming League as part of the
Toronto Titans.
World Swimming Championships McIntosh was part of the Canadian team for the
2021 World Swimming Championships in
Abu Dhabi, and won a silver medal as part of the
4×100 metre medley relay, where she swam in the preliminaries for Canada as the team finished in second in the final. She then helped the Canadian team in the
4×200 metre freestyle relay, swimming the first leg as Canada won gold. McIntosh won her first individual medal of the competition when she won the silver in the
400 metre freestyle race. She was third at the halfway mark but passed
Siobhán Haughey and held on to the second position, finishing behind
Li Bingjie. McIntosh had set a
Canadian record in the
800 metre freestyle heats, but she withdrew from the event to focus on the 400 and women's relay events.
2022 season On March 4, 2022, McIntosh swam the 400 metre individual medley at a preparatory event for the Canadian swimming trials, recording a time of 4:29.12. This was both a national and
Commonwealth record, and the third-fastest of all time, as well as the fastest time recorded by any swimmer since
Katinka Hosszú's winning time at the
2016 Summer Olympics. At the national swimming trials, McIntosh won titles in the 200 metre and 400 metre freestyle, the 200 metre butterfly, and the 400 metre individual medley, before scratching from the 800 metre freestyle.
World Championships McIntosh made her long course (50m)
FINA World Aquatics Championships debut at the
2022 edition in
Budapest, with her first event being the
400 metre freestyle. She finished second in the final, taking the silver medal with a new personal best and
national record time of 3:59.39. She was only the fourth woman in history to record a time of under four minutes. McIntosh set another world junior record in the semi-final of the
200 metre butterfly with a 2:05.79 time, exceeding her own as-yet-unratified record from the Canadian swimming trials. She broke the record again the following day, June 22, in the event final, claiming her first World title, the first medal of any colour for Canada in the event. She was the first 15-year-old to win a World title since China's
Ye Shiwen in
2011, and the youngest Canadian world champion in history, surpassing 18-year-old
Victor Davis in
1982. Later in that same session she participated in the event final of the
4 × 200 metre freestyle relay, breaking another junior world record with a 1:54.79 opening leg, the second-fastest of any woman in the event behind
Katie Ledecky of the United States. The Canadian team won the bronze medal. As well, she was the youngest winner since
Tracy Caulkins in
1978. McIntosh called the results "a dream come true", and praised Grimes, noting "she is around my age and she's a really tough competitor. So I'm looking forward to racing her and keep pushing myself."
Commonwealth Games A month later, McIntosh was part of her first
Commonwealth Games team, for the
2022 edition in
Birmingham,
England. She opted not to contest the 200 metre butterfly there, citing the need to focus on other events. Heavily favoured in the
400 m medley, she won gold on the first day of the competition schedule, improving her world junior, Commonwealth, and national records to 4:29.01. She finished 7.77 seconds ahead of silver medallist
Kiah Melverton, and was the first Canadian gold medallist of the Games. McIntosh was then given the novel opportunity to participate in Canada's
4 × 100 metre freestyle relay team, with mainstay members like Oleksiak, Sanchez and
Taylor Ruck absent, winning a bronze medal. She noted that she "didn't really know what to expect, the 100 free is not my main event so I just tried to put a good time down to set it up for the rest of the girls." The next day she took her more customary place on the
4 × 200 metre freestyle relay team, swimming the leadoff leg and helping take the silver medal. Of this, she said she was "very proud." On the fourth day, she competed in the
200 metre individual medley, a much more uncommon event for her than the 400 metre individual medley. McIntosh won the gold medal, defeating reigning World silver medallist
Kaylee McKeown of Australia and setting a new world junior record. McIntosh noted that "the 200 IM is more of a sprinting event for me", adding "the only pressure I feel is what I put on myself. The only thing that matters is my expectations." With the result, McIntosh recorded one of the top four results of 2022 in five different events. On the final day of the swimming competitions, McIntosh won two more silver medals, finishing behind
Ariarne Titmus in the
400 metre freestyle while lowering her own national record and then swimming the freestyle leg of the
4 × 100 metre medley relay, typically performed for the Canadian team by the absent Oleksiak. Following the conclusion of the Commonwealth Games,
Swimming World magazine, assessing her "vast talent on display at two championship-level events", opined "it's not hype and bluster anymore. Based purely on results from this year, not career medal totals or performance over a long stretch of time, McIntosh is the third-best female swimmer in the world." The following day, she won the gold medal in the 400 metre individual medley with a world junior record and Canadian record time of 4:21.49. She and fellow Canadians
Sydney Pickrem and
Bailey Andison won all the medals in the event. The following, and final, day, she won a pair of bronze medals, the first in the 200 metre backstroke with a personal best time of 2:02.85 and the second in the 200 metre individual medley with a personal best time of 2:06.57. The next, and final, stop of the World Cup circuit, McIntosh won the gold medal in the 200 metre butterfly on November 3, finishing in a personal best time of 2:03.40, which was the only time in the final faster than 2:04.00. Day two, she finished in a personal best time of 1:52.63 in the 200 metre freestyle final to place fifth. On the third and final day, she dropped 6.25 seconds from her personal best time in the 800 metre freestyle to win the silver medal with a Canadian record time of 8:07.12. The following month, at the
2022 U.S. Open Swimming Championships, McIntosh won the gold medal in the 400 metre individual medley with a
Championships record, world junior record, and
US Open record time of 4:28.61. The following day, she won the silver medal in the 200 metre backstroke with a personal best time of 2:07.15, which was 1.87 seconds behind gold medallist
Regan Smith of the United States. Earlier in the meet, on day two, she won the silver medal in the 400 metre freestyle. Days later in the 200 metre freestyle event, she broke
Taylor Ruck's national record and lowered her prior world junior record with a time of 1:54.13, and won the event over
Katie Ledecky. This was the first time Ledecky had lost a domestic final in the 200 metre distance or higher since 2014. McIntosh remarked that "I'm really happy with that swim but it hurts really bad." She then broke
Sydney Pickrem's national record in the 200 metre individual medley. At the national swim trials at the end of March at the
Toronto Pan Am Sports Centre, McIntosh set her first
world record, winning the 400 metre freestyle event with a time of 3:56.08 seconds and surpassing
Ariarne Titmus's prior time of 3:56.40. Speaking afterward, she said that "going into tonight, I didn't think the world record was a possibility, but you never know." Days later, McIntosh won the 400 metre medley with a time of 4:25.87, breaking the world record that
Katinka Hosszú had set at the
2016 Summer Olympics. She became the first swimmer in history to hold both the 400m freestyle and 400m individual medley long course world records at the same time. McIntosh also improved her own world junior records in three other events at the meet.
World Championships McIntosh's first event of the
2023 World Aquatics Championships in
Fukuoka was a highly-anticipated
400 metre freestyle, touted as a three-way contest between her, Titmus and Ledecky. She came third in the heats, but in the final she finished narrowly in fourth place, being overtaken for bronze in the final stretch by New Zealander
Erika Fairweather. McIntosh called it a "learning experience." Later the same session she joined the Canadian team in the final of the
4×100 metre freestyle relay; with Oleksiak absent and Ruck recovering from a hand injury, the team finished seventh. McIntosh competed in the
200m freestyle at the World Championships for the first time, finishing second in the semi-finals, 0.03 back of Titmus and 0.24 ahead of
Mollie O'Callaghan. She came third in the event final, out touching reigning Olympic silver medallist
Siobhan Haughey for the bronze. On July 27, McIntosh successfully defended her title in the
200m butterfly and improved on her world junior record in the event, claiming that she "was just trying to have as much fun as possible and race as hard as I could." She became only the second Canadian to win three World titles, after
Kylie Masse, as well as the second to defend a World title, again after Masse. Later in the day she joined the Canadian team in the final of the
4×200 metre freestyle relay. The team, depleted of some of its most important members from years prior, finished in fifth, but McIntosh's 1:53.97 was the second-fastest in the event, behind Titmus, and the ninth-fastest of all time to that point. After finishing second in her heat for the
400m medley, McIntosh defended her title, winning in
championship record time (4:27.11) and a margin of 4.30 seconds over repeat silver medallist
Katie Grimes. In so doing, she broke her tie with Masse for sole possession of the record for Canadian World Aquatics titles. Later in the same session, she swam the freestyle leg of the
4×100 m medley relay, helping the team to a bronze medal. Her 53.48 time was an improvement by almost a second and a half over her performance in the earlier freestyle relay. In her final major competition of the year, the
2023 U.S. Open Swimming Championships, McIntosh won the gold medal in the 400m freestyle race, defeating Ledecky and breaking the latter's championship record with a time of 3:59.42. She went on to defend her gold medal in the 400m individual medley, defeating Israeli silver medallist
Anastasia Gorbenko by almost eight seconds. McIntosh was a finalist in voting for the
Northern Star Award, given to the Canadian athlete of the year, and received the
Bobbie Rosenfeld Award as
the Canadian Press' choice for Canadian female athlete of the year.
2024 season As with most of the Canadian team's top swimmers, McIntosh opted not to attend the
2024 World Aquatics Championships in
Doha, citing its proximity to the
2024 Summer Olympics. She drew headlines in early February when she defeated
Katie Ledecky at a sectional event in
Orlando, becoming the first person to outpace Ledecky in the 800 metre distance since 2010. Her 8:11.39 time broke a ten-year-old national record previously set by
Brittany MacLean at the
2014 Pan Pacific Swimming Championships. At the inaugural edition of the Canadian Swimming Open in April, McIntosh won the 200m freestyle with a world-leading time of 1:54.21. She came in second in the 100m backstroke final later in the same session, finishing just behind
Maggie Mac Neil. She would go on to win the 100m freestyle, 100m butterfly, and 200m individual medley. McIntosh was the centre of attention at Canada's Olympic swimming trials, which featured audiences, unlike in the pandemic-afflicted 2021 events. On the first day, she won the 400m freestyle with a world-leading time that she nevertheless said she was "definitely not happy with." She then won the 200m freestyle on the second day. McIntosh drew headlines on the fourth day in the 400m individual medley, where she broke her own world record with a 4:24.38, an improvement of a second and a half. She finished more than fourteen seconds ahead of second-place
Ella Jansen. In her fourth event of the trials, the 200m butterfly, she posted a world-leading time of 2:04.33. On the final day of the trials, McIntosh won the 200m individual medley, and was formally named to
the Canadian Olympic team.
Summer Olympic Games McIntosh competed in the
400m freestyle,
400m individual medley,
200m butterfly,
200m individual medley,
freestyle relay,
freestyle relay, and the
medley relay at the
Paris 2024 Olympics. The 400m freestyle was first, in which McIntosh,
Ariarne Titmus, and
Katie Ledecky were the favourites to compete for gold. McIntosh won the silver medal, finishing 0.88 seconds behind Titmus. This was her first Olympic medal and the first Canadian medal in Paris. Later in the same session McIntosh participated in the final of the
freestyle relay, where the Canadian team finished fourth. Her next event was the 400m individual medley, where she was the heavy favourite. She won the gold medal, finishing more than five seconds ahead of American silver medallist
Katie Grimes to take her first Olympic title. It was the first time a
Canadian had ever won the event, and McIntosh said after the race that winning the gold felt "surreal."
CBC Sports wrote that it was a "dominating victory", This was the second-fastest time in the history of the women's 200m butterfly, and the fastest of the
textile era. McIntosh became the first Canadian woman to win two individual gold medals at a Summer Olympics, the first Canadian to win two gold medals at a Summer Olympics since sprinter
Donovan Bailey in
1996, and the first Canadian swimmer to win three individual medals at a single Olympics. In the same session she joined the Canadian team in the final of the
4×200m freestyle relay, where they finished fourth, a result she said she was "pretty disappointed with." This was only the second time that she had appeared in the 200 metre medley at an international competition, after the 2022 Commonwealth Games. Considered one of the favourites, she won the title with an Olympic record time of 2:06.56. She became the first Canadian to win three gold medals at a single Summer Olympics, and with four total medals she tied teammate
Penny Oleksiak for the most Canadian medals in a single Olympics. McIntosh's final swim of the Paris Olympics was as part of the Canadian team in the
medley relay, having replaced Oleksiak as the anchor for the event final. For the third time, the Canadians finished fourth, denying McIntosh's chance to tie
Cindy Klassen's record for the most medals won by a Canadian Olympian in a single Olympics. Following the end of the Olympic swimming competitions, she returned to Canada to vacation at her family's
Muskoka Lakes cottage, but travelled back to Paris a few days later upon being named Canada's co-flag bearer at the
closing ceremony, alongside
hammer throw champion Ethan Katzberg.
World Swimming Championships and recognition It was announced that McIntosh would compete at the short course (25m)
2024 World Aquatics Swimming Championships, her first appearance in this World Championships format since 2021. On the first day of the event, McIntosh swam to gold in the
400m freestyle, setting a new short course world record of 3:50.25 and lowering it by over a second in the process. Later in the same session she participated in the
4×100m freestyle relay, earning a bronze medal with the Canadian team. On the same day, she was voted the recipient of the
Northern Star Award as Canada's top athlete for 2024. She won another gold medal in the
200m butterfly, setting a second short course world record by breaking Spaniard
Mireia Belmonte's decade-old best time. On the penultimate day of the championships she won gold in the
400m individual medley, breaking the last of Belmonte's world records and improving on it by over three seconds for a time of 4:15.48. On the final day, McIntosh contested the
200m backstroke, the first time she had appeared in that event at a major international championship. She took the silver medal and set a national and world junior record time of 1:59.96. McIntosh expressed disappointment with the result, but added that it was "a great motivator the next time I'm training and I'm hurting and I just remember what it's like to get silver, so it keeps me pushing forward." At the conclusion of the meet,
World Aquatics named her
female swimmer of the year. In addition to the
Northern Star Award and
World Aquatics athlete of the year, McIntosh received her second consecutive
Bobbie Rosenfeld Award as the
Canadian Press's choice for female athlete of the year, winning 52 of 53 votes cast for the distinction. She was named to the
Time 100 Next list, with a tribute written by
Prime Minister Justin Trudeau, who described her as "a superstar at age 18 and still warming up."
Forbes included McIntosh in their year-end
30 Under 30 list.
2025 season In February, McIntosh raced in the 800m freestyle at the Southern Zone Sectionals meet, setting a new national record time of 8:09.86. This was the tenth-fastest time in history, the nine times ahead of hers all having been set by
Katie Ledecky. At the end of the month, she announced that this would be her final season training in
Sarasota under
Brent Arckey, and that she was contemplating working with
Bob Bowman in the future. As well, she stated she would be looking to add a fifth individual event to her program for the
2025 World Aquatics Championships. On May 28, McIntosh confirmed that she would move to train under Bowman at the
University of Texas at Austin in August of that year. On June 7, McIntosh regained the world record in the women's 400m freestyle event at the Canadian swimming trials with a time of 3:54.18. Then, on June 8, she improved her national record in the 800m freestyle from an 8:09.86 to a 8:05.07. On the following day, she broke
Katinka Hosszú's decade-old world record in the 200m individual medley with a time of 2:05.70, becoming the first woman with a time under 2:06. On June 10, she lowered her own national record in the 200m butterfly with a time of 2:02.26, and became the second-fastest performer of all time, in this event. On the second day, she swam the final of the
200m individual medley, her first appearance in the event at the World Aquatics Championships. McIntosh won her second gold medal of the Singapore championships with a time of 2:06.69. This was her tenth World Aquatics Championships medal, surpassing
Kylie Masse and
Penny Oleksiak for the most earned by a Canadian swimmer. McIntosh entered the
200m butterfly as the prohibitive favourite for the gold medal, with speculation focused on whether she would break the world record of 2:01.81, set in 2009 by
Liu Zige using a "
supersuit" that would be prohibited from World Aquatics competition three months after. As a result of this, Liu's record became the longest-standing record in women's competitive swimming. McIntosh won with a time of 2:01.99, three seconds ahead of silver medalist
Regan Smith. She was 0.18 seconds short of the world record, but broke
Jessicah Schipper's supersuit era championship record from
2009. McIntosh faulted herself, saying "that last 15 metres I took an extra breath and I should've had my head down," but vowed "this is definitely going to fuel me for next season," adding: "If there's one world record that I wanted to break since the start of my career it's this one." McIntosh held the lead at the 700-metre mark, but was passed by both Ledecky and
Lani Pallister over the closing stretch, winning the bronze medal. She called the race "not even close to what I wanted time-wise, place-wise, how I executed the race." McIntosh was named Female Swimmer of the Meet by World Aquatics.
U.S. Open McIntosh initially planned to compete in the
2025 World Aquatics Swimming World Cup in October, but then pulled out of the
Carmel stop because of illness, subsequently revealed to be consequences of a
lumbar puncture. She ultimately withdrew from the remainder of the Swimming World Cup, including her hometown of Toronto. winning two events and finishing third in another. At the end of the year, McIntosh finished second in balloting for the Northern Star Award, behind basketball player
Shai Gilgeous-Alexander, and received her third consecutive Bobbie Rosenfeld Award as Canadian female athlete of the year. On December 30, World Aquatics named her the Female Swimmer of the Year for a second consecutive time.
2026 season In January, McIntosh secured victories in two events during the first leg of the Pro Series held in Austin. She also competed in the Westmont leg, winning three. ==Results==