Petr Kellner, the Czech Republic's richest man and founder of investment group PPF, was killed in a helicopter crash on a skiing trip in Alaska.
Kellner, 56, was among the five, including the pilot, killed on Saturday in the crash near Knik Glacier northeast of Anchorage, Alaska State Troopers said.
One survivor was taken to hospital, they said, adding the group had been on a heli-ski tour.
Kellner, who avoided public attention, was featured in one PPF annual report on a snowboard.
A spokeswoman for the exclusive Tordrillo Mountain Lodge, where the crash victims were staying, said Kellner had been a frequent guest since 2012.
Kellner was a towering figure in the Czech Republic's post-communist era, amassing wealth estimated at $17.5 billion according to Forbes.
He was the world's 68th richest person on Forbes' 2020 list, tied with media giant Rupert Murdoch and his family.
PPF in a statement expressed "deepest grief" at the death of its founder and 98.9% shareholder.
Ladislav Bartonicek, a 30-year PPF veteran who owns just over a 0.5% stake, will take over management duties, the company said.
PPF's third shareholder, Jean-Pascal Duvieusart, also with just over 0.5%, said the company would continue building and keeping with Kellner's vision.
"Petr was somebody who was truly extraordinary in terms of energy, in terms of creativity, in terms of a drive to build new things," Duvieusart said in a telephone interview.
Kellner is survived by his wife Renata and four children.
He started out selling copy machines as the country opened up following the 1989 Velvet Revolution. He set up PPF with partners for the country's privatisation programme.
With holdings in finance, telecommunications, manufacturing, media and biotech, PPF reported assets of 44 billion euros ($51.8 billion) in mid-2020.
PPF controls telecoms firms in central and eastern Europe including O2 Czech Republic, Telenor CEE and CETIN.
Its biggest firm is consumer lender Home Credit, active in markets including Russia, China and India.
Home Credit was an early entrant into China market, starting lending there as the first fully foreign-owned firm in 2010.
Its business there was championed by Czech leaders, which critics saw as a turning away from the country's human rights diplomacy course set by the first post-communist leader, Vaclav Havel.
President Milos Zeman has sought warm relations with China and took Kellner into a meeting with Chinese President Xi Jinping in 2014.
Kellner also financed a thinktank set up by former President Vaclav Klaus, architect of the 1990s privatisation that allowed Kellner's business rise.
"His life story was an example of harnessed opportunity offered to young people by the economic transformation," Klaus said.
Kellner had recently focused on his home market, with PPF acquiring a stake in MONETA Money Bank and proposing merging it with its Air Bank and parts of Home Credit. MONETA shares fell 1.7% on Monday.
Last year, PPF completed the acquisition of Central European Media Enterprises, a group of television stations, from Time Warner.