"We lost Mustafa Koc despite all efforts by doctors as a result of a heart attack he had at his home," the American Hospital in Istanbul said in a statement.
Koc was the leader of the third generation of one of Turkey's biggest industrial dynasties, founded by his grandfather Vehbi Koc in the 1920s.
Under Vehbi Koc and his son Rahmi, the Koc conglomerate expanded to become the most important of the holding companies that dominate Turkish industry, with diverse interests in energy, banking and the automobile sectors.
It also has a thriving auto industry joint venture with Ford (Ford Otosan) and with Fiat (TOFAS).
Also Read
Mustafa Koc took over as chief executive of Koc Holding in 2003. He is survived by his father Rahmi Koc, 85. Founder Vehbi Koc died in 1996 aged 94.
The Hurriyet daily said Mustafa Koc had arrived in Istanbul late yesterday after a trip to Ankara where he met President Recep Tayyip Erdogan in an unpublicised meeting.
He had been due to fly to the World Economic Forum in Davos later today. Reports said Koc had suffered the heart attack during a morning workout.
Koc Holding and some 100 subsidiaries alone account for around nine percent of Turkish exports and eight percent of its GDP.
The family is one of the richest in Turkey: according to 2015 estimates by the Turkish edition of Forbes magazine, Mustafa Koc had a fortune of over USD 1 billion and his father Rahmi USD 2.5 billion.
"He was a smart man and an honest man. He has lost his life very young and we are in shock today," Guler Sabanci, chairperson of the rival Sabanci Holding, told CNN-Turk.
"We have lost one of our most successful, energetic and productive sons," added Finance Minister Mehmet Simsek on Twitter.