Sergio Marchionne, a master negotiator who engineered one of the most brazen automotive deals in history when he persuaded the U.S. government to sell bankrupt automaker Chrysler to Italy’s Fiat, and turned the combined Fiat Chrysler into one of the most profitable firms in the industry in less than a decade, died July 25 at a hospital in Zurich. He was 66.

The news agency ANSA reported that the cause was cardiac arrest following shoulder surgery. Mr. Marchionne had already planned to retire next year and turn the reins over to successor Mike Manley, who led the company’s Jeep and Ram brands.

There appeared to be a sense of frenzied panic about what comes next for the company Mr. Marchionne had expanded with astonishing success, much of it credited to his charismatic personality, frank disposition, negotiating prowess and indefatigable work ethic.

He also represented a fundamental shift for Fiat and the wider landscape of Italian industry. He was the first person outside the Agnelli clan to be at the helm of Turin-based Fiat, and — as the son of an Italian immigrant to Canada — was not groomed within the rarefied cliques that have dominated Italy’s industrial and banking sectors for generations.

The Italian-born, Canadian-raised Mr. Marchionne vaulted to instant fame in auto circles at the peak of the U.S. financial crisis in 2009, when he wedged himself into the center of negotiations in Washington about what to do with failing auto giants General Motors and Chrysler, both on the brink of bankruptcy.

Mr. Marchionne became involved with President Barack Obama’s Auto Task Force, which had the mandate to analyze the two companies and manage any possible bankruptcies. Mr. Marchionne convinced task force officials that Fiat, which he had run for only five years, was the right partner for Chrysler.

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On April 30, 2009, Chrysler filed for bankruptcy. On June 10, Fiat and Chrysler announced the merger of the two companies, with Mr. Marchionne emerging as chief executive and, in the eyes of many, the savior of one of Motor City’s legacy companies.

“So the industry looks like it’s going to sink into oblivion and this fellow who wears this black sweater, chain smokes and drinks gallons of espresso manages to insert himself and convince these people that the best alternative for Chrysler is to merge with Fiat,” said Maryann Keller, a leading automotive industry analyst. “On its own, it doesn’t make any sense.”

Mr. Marchionne engineered a brilliant deal for Fiat, Keller said.

The initial terms gave Fiat a 20 percent stake in Chrysler, with the U.S. and Canadian governments, along with the United Auto Workers Union, holding the rest. But the Italian carmaker could claim more equity if it met two requirements.

First, the company would have to assemble in North America a small car that would be fuel-efficient at a time of rising gasoline prices. Second, it would have to build a small, fuel-efficient engine on U.S. soil. In exchange, Fiat would get control of Chrysler, free from liability, without paying a dime.

“They gave away the store,” Keller said, adding that the two manufacturing demands put on Fiat were paltry compared with what Fiat got in return: billions of dollars in Chrysler assets and intellectual property.

But speaking to CBS’s “60 Minutes” in 2012, Mr. Marchionne said taking on a failing company was a tall order.

“All these things are long shots. All,” he said. “If it was that easy, then everybody would do it.”

Mr. Marchionne found the key ingredients to the relaunch of an automotive giant, starting with a restructuring of the business.

He separated the pickup trucks from the Dodge brand and formed an entirely new pickup line called Ram, whose trucks were marketed for size, engine strength and fast acceleration.

That brand, along with the Dodge line, which he successfully reimagined as the maker of a new American muscle car, has taken off in the U.S. market.

The Jeep brand also thrived under his helm, selling globally and giving Fiat Chrysler a footprint in China, the world’s biggest auto market.

Mr. Marchionne changed the management structure at Chrysler — a signature tactic he had used throughout his career — and refused to sit in the chairman’s office on the top floor.

“I’m on the floor with all the engineers,” he said in the “60 Minutes” interview. “I can build a car with all the guys on this floor. That’s all I care about.”

In his 2015 analysis of the auto industry, “Confessions of a Capital Junkie,” Mr. Marchionne said consolidation was inevitable to promote efficiency. It was folly, he said, for carmakers to invest so much developing near identical technologies. He tried for another merger with General Motors, but the talks never advanced.

Perhaps Mr. Marchionne’s biggest victory was recasting Chrysler in a positive light after its bankruptcy, positioning the company as a gritty, born-from-the-ashes American survivor. A 2011 Super Bowl commercial for Chrysler featured Detroit native and rapper Eminem and the slogan “Imported from Detroit.”

“He captured the attention of the auto market in ways others would be timid about,” Keller said of Mr. Marchionne. “He made it cool.”

Sergio Marchionne was born in Chieti, Italy, on June 17, 1952. His father was a member of the paramilitary Carabinieri police who later moved the family to Toronto to be near relatives and offer his two children more opportunities. (Mr. Marchionne’s sister, Luciana, died of cancer in 1980, according to Canada’s Globe and Mail newspaper.)

The assimilation in Canada, in his teens, was not easy at first. “Trying to get friendly with girls with whom you cannot communicate was a problem,” he told the paper.

He received a bachelor’s degree in philosophy in 1978 from the University of Toronto, where he also obtained a bachelor’s degree in commerce the next year. He completed a law degree from Toronto’s York University in 1983 and a master’s degree in business from the University of Windsor in 1985.

Mr. Marchionne had two children with his first wife, Orlandina, from whom he was separated. Other survivors include his companion, Manuela Battezzato.

After working as an accountant and tax officer at Deloitte & Touche in Toronto, Mr. Marchionne served in executive roles for the Toronto packaging company Lawson Mardon Group and other firms from 1985 to 2000. In 2002, he was named chief executive of a Swiss testing and certification company and the next year joined the board of Fiat’s holding company. He later became the holding company’s chief executive and, in 2006, was made chief executive of Fiat’s auto division.

He immediately began a turnaround of the troubled carmaker, cutting costs and whipping it into shape financially. By 2009, he was in Washington, negotiating one of the biggest auto deals of his era. Within two years, Chrysler made its first profit ($183 million) since 2005 and paid back its $6 billion federal bailout six years before it was due.

“I remember when I came here in 2009,” he told “60 Minutes” in 2012. “There’s nothing worse for a leader than to see fear in people’s faces. It’s been a long, rocky road, but the fear is gone.”

Brian Murphy contributed to this report.