World 800m champion Pierre-Ambroise Bosse sustained "multiple facial fractures" after a vicious late-night attack in the southwest Gironde region of France last weekend.
Bosse, 25, said on his Facebook page Wednesday that he was the "victim of a violent attack" while on holiday and had been "brutally assaulted by three individuals".
He said he had suffered "unspeakable psychological damage" as a result of the incident and had been forced to put an early end to his season.
"Me who has always loved people, I love three less of them today," Bosse wrote.
A police investigation is continuing after a complaint was filed, with authorities still on the hunt for the assailants.
According to the website of the Sud Ouest newspaper, the attack occurred at around 4:00 am (0200 GMT) on Sunday morning in the car park of the Gujan-Mestras casino.
Bosse had reportedly spent the night out with friends when he was approached by the three people, posing for a photo alongside them before events turned sour.
At the world championship final in London this month Bosse produced a stunning burst with 150m to go to give France their first-ever gold in the 800m.