It was a game with a goal when the teenager with great expectations on her shoulders secured her first Olympic Games gold in her career.
The Canadian world record holder fired off a gold smile and waved to the TV cameras after swimming to the finish line in 4:27.71.
I'm very happy to succeed in reaching the top of the podium and winning gold, she says in the mixed zone where swimmers meet the press.
McIntosh was over three seconds above her own world record, but still outclassed her competitors.
Second place Katie Grimes, USA, was beaten by 5.69 seconds.
The bronze also went to the USA through Emma Weyant.
Chasing more gold
McIntosh took silver on Saturday in the star-studded 400-meter freestyle with gold winner Ariarne Titmus, Australia, and American veteran Katie Ledecky who had to settle for bronze.
The Canadian can become one of the Olympic Games' big winners and is chasing two more golds on the 200-meter medley and 200-meter butterfly.
The 17-year-old Canadian is from a real sports family. Her mother Jill Horstead was herself an Olympic swimmer and older sister Brooke competes in figure skating.
Two years ago, McIntosh left her hometown Toronto to train and compete for the classic swim club Sarasota Sharks in Florida.
McIntosh, who turns 18 in August, made her Olympic debut in Tokyo 2021 at just 14 years old and over the next two years broke through big time, taking a World Championship double gold in both 2022 and 2023 on the 400-meter medley and 200-meter butterfly.
Historic Romanian gold
Also on the men's 200-meter freestyle, a teenager won.
Romanian star David Popovici drew the longest straw in a hundredth-of-a-second thriller and became historic as the first Romanian male swimmer to take Olympic Games gold.
The 19-year-old won by two hundredths of a second ahead of 2023 World Championship gold medalist Matt Richards, Great Britain, and third place Luke Hobson, USA, was only seven hundredths of a second behind Popovici.
The Romanian broke through with double World Championship gold in 2022 on the 100 and 200-meter freestyle, but didn't get it together last year and missed World Championship medals on both distances.
Now he's back.
