Sergio Marchionne, who engineered a merger of the auto industry’s weakest companies—Fiat and Chrysler—and turned the combination into a profit generator, died at the age of 66.

Mr. Marchionne was treated at Zurich’s University Hospital for complications after undergoing what Fiat Chrysler Automobiles NV said was a surgical procedure on his right shoulder in July. The health issues forced the company to unexpectedly remove him as CEO on Saturday, speeding up a departure planned for early 2019 after a decade at the helm of the Italian-American auto maker.

Exor SpA, the company that controls Fiat Chrysler, on Wednesday announced Mr. Marchionne’s death.

While less known among the general public than predecessors such as Lee Iacocca, Mr. Marchionne was a star in the auto industry, and his death marks an end of an era in Detroit where he was one of the last larger-than-life CEOs. He relished challenging auto industry orthodoxy, and was ahead of rivals on some key automotive trends.

In a tweet late Wednesday, President Donald Trump called Mr. Marchionne “one of the most brilliant and successful car executives since the days of the legendary Henry Ford.” Broker Evercore ISI called him “one of the most formidable and successful CEOs in the industry’s history.”