Chef Benoit Violier, whose Swiss restaurant was named the best in the world in December, has been found dead at his home.
Mr Violier, 44, ran the Restaurant de l’Hotel de Ville in Crissier, near the city of Lausanne.
It earned three Michelin stars and came top in France’s La Liste ranking of the world’s 1,000 best eateries.
Swiss police said Mr Violier, who was born in France, is believed to have killed himself.
The Swiss news website 24 Heures said (in French) that Mr Violier had been due to attend the launch of the new Michelin guide in Paris on Monday.
His death comes some six months after that of Philippe Rochat, his mentor and predecessor at the Restaurant de l’Hotel de Ville.
Having worked at the restaurant since 1996, Mr Violier took it over along with his wife Brigitte in 2012, before obtaining Swiss nationality.
A keen hunter, he was known for signature dishes including game and produced a weighty book on game meat last year.
Accepting the French award, given by France’s foreign ministry as an alternative to the World’s Best 50 Restaurants prize, he said it was an “exceptional” honour.
Swiss chef Fredy Girardet, who also received three Michelin stars, told 24 Heures that he was “dumbfounded” by the news.
“He was a brilliant man,” he said. “Such talent, and an amazing capacity for work. He was so kind, with so many qualities. He gave the impression of being perfect.”
French chef Pierre Gagnaire tweeted: “My thoughts go out to Benoit Violier’s family. Very sad news about an extremely talented chef.”