The 13-year-old clocked 4:28.56, shattering the previous Asian Games record set by compatriot Ye Shiwen in 2014 by approximately 4.5 seconds. It was also the fourth-fastest time in the world this year.
Yu had already won the 200m butterfly and 200m individual medley, both in Games-record times, making her one of the standout performers of the swimming competition in Tokyo.
She took the lead from the start in the 400m IM and finished nearly four seconds clear of silver medallist Ke Wenxi (China), with Japan’s Mio Narita taking bronze.
Yu first gained international attention last year when she became the youngest medallist at the World Aquatics Championships at the age of 12, winning bronze in a relay. She has continued to impress, including a notable victory over American Olympic medallist Regan Smith in the 200m butterfly earlier this year.
With the Los Angeles 2028 Olympics still two years away, the teenage prodigy is already being tipped as a major medal contender on the global stage. Her performances in Tokyo have also made her a major sensation back home in China.