Jim Cantalupo, chief executive and chairman of fast-food chain McDonald's, has died of an apparent heart attack.
Under Jim Cantalupo's leadership McDonalds turned itself around
The company said the 60-year-old had been attending a meeting of restaurant franchise owners in Orlando, Florida, when he fell ill.
Mr Cantalupo, who took over the reins of the company in January 2003, had been widely praised for turning around its then flagging fortunes.
McDonald's has named Charlie Bell as Mr Cantalupo's successor.
Mr Bell was previously the company's president and chief operating officer.
Under Mr Cantalupo's leadership McDonald's posted its highest sales gain in 30 years.
Its shares fell by 80 cents or 2.9% to $26.66 after Monday trading started on Wall Street following the announcement of his death.
In a statement, McDonald's said Mr Cantalupo was "a brilliant man, who brought tremendous leadership, energy and passion to his job".
"He made an indelible mark on McDonald's system," it added.
Mr Cantalupo was credited with turning around McDonald's since he was brought back from retirement to lead the company in January 2003.
He had retired a year earlier after 28 years with the company.
A former vice-chairman and president, his focus on introducing new items such as salads and grilled chicken - in the face of criticism that its traditional products were too high in fats, salt and sugar - saw revenues recover.
And this came against a backdrop of the mad-cow disease scare in the US, which put many consumers off eating beef.
Mr Cantalupo also saw McDonald's slow down its historically high-speed expansion and the closure of hundreds of under-performing restaurants.
"The worries are that perhaps there may not be a strong number two, since he was known as the one with the strong vision," said Art Hogan, chief market analyst for investment adviser Jefferies & Co.
Only last week McDonald's introduced a new Adult Happy Meal in the US that included a pedometer to encourage people to walk more.