He won the 50 metre backstroke at three consecutive world championships (2013 Barcelona, 2015 Kazan, and 2017 Budapest).

He became European Champion in the 100 m backstroke (long course) ahead of compatriot Jérémy Stravius in a time of 52.11.

Following his 5th-place finish in the 100 meter backstroke, Lacourt made international news after criticizing the sport of swimming and making disparaging remarks about Chinese swimmer Sun Yang.

In a post-race interview with French radio station RMCsport, Lacourt said: "I am very sad when I see my sport getting like this.

I hope that FINA is going to react and stop this massacre, because it is getting sad," and finished with "Sun Yang, he pisses purple!