The 13-year-old won her third straight gold when she won the 400-meter medley in Nagoya, Japan.
The winning time of 4:28.56 was less than five seconds off Canadian Summer McIntosh's world record of 4:23.65.
Yu Zidi, who turns 14 in October, has previously won both the 200-meter butterfly and 200-meter medley.
Last year, she became the youngest swimmer to win a World Championships medal, when at the age of 12 she was part of China's bronze-winning 4x200-meter freestyle team.
Her spectacular success has also sparked discussion about how the extensive amount of training can affect her, both physically and mentally, at her young age.
What do you think?