Mayer (30), also a double Olympic silver medalist (2016 and 2021), totaled 8,816 points after ten events to win ahead of Canadian Pierce Lepage (8,701) and American Zachery Ziemek (8,676).
The reigning Olympic champion, Canadian Damian Warner, had given up in the middle of the 400m at the end of the first day, hit in the left thigh.
At the age of 30 – he celebrated them in February – Mayer joined the ultra-select club of French athletes, double individual world champions, alongside the legend Marie-Josée Pérec, crowned in the 400m in 1991 and 1995, and Eunice Barber, she crowned in the heptathlon in 1999 and in the long jump in 2003.
Midway through the previous evening, Mayer was in sixth position, some 200 points behind the provisional leader, Puerto Rican Ayden Owens-Delerme.
After a good 100m and a performance in his standard at length, the world record holder (9126 points in 2018) had missed his shot put at midday, with a best throw at 14.98m, very far from his record (17.08m).
Under a hot sun on Sunday, the Montpellier player built his rise in the standings on the pole (5.40 m) and the javelin (beyond 70 m) in particular.
Even if he had a fright at the pole, when he found himself with his back to the wall from 5 m, finally crossed on his third and last try.
As a symbol, he had experienced a similar scenario on his way to his first world title in London in 2017, this time at 5.10m.
Mayer, bothered by his right Achilles heel for long weeks at the start of the year and who had therefore given up the Indoor Worlds in early March in Belgrade, was competing in his first decathlon since the Tokyo Olympics crossed back blocked in the summer. last.