Marchionne was born in Chieti, Abruzzo, Italy. His father served as a Carabiniere in Istria, where the family had deep roots; his maternal grandfather was killed in 1943 during the wartime upheaval in that region. In 1965, at the age of thirteen, Marchionne emigrated with his family to Toronto, Ontario, Canada, where he would build both his education and his career.
He attended St. Michael's College School before completing undergraduate studies in philosophy at the University of Toronto. He subsequently earned a bachelor of commerce degree (1979) and an MBA (1985) from the University of Windsor, and a law degree from Osgoode Hall Law School of York University (1983). He carried dual Canadian and Italian citizenship and spoke fluent English, French, and Italian.
Marchionne began his professional life as an accountant and tax specialist at Deloitte and Touche in Canada from 1983 to 1985. He then moved through a sequence of senior finance and management roles at the Lawson Mardon Group, Glenex Industries, Acklands Ltd, and the Algroup industrial conglomerate, eventually becoming CEO of Algroup in 1997.
In 2002, he became CEO of SGS S.A., the Geneva-based inspection and certification company, where he was later appointed chairman. His reputation for decisive restructuring drew the attention of the Agnelli family, and in 2003 he joined the Fiat board, becoming CEO of Fiat S.p.A. in 2004. Within less than two years he transformed Fiat Group from a company on the verge of collapse into one of the fastest-growing automakers in the world, a feat that established his standing as one of the boldest executives of his generation.
When Chrysler emerged from Chapter 11 bankruptcy protection in June 2009, Fiat Group received a 20 percent stake in the restructured company and Marchionne was appointed its CEO, replacing Robert Nardelli. He worked in close alignment with the United States and Canadian governments to return Chrysler to profitability — the company repaid government loans ahead of schedule.
In 2011 he made international headlines when he described Chrysler's bailout loan interest rates as carrying "shyster rates" at an industry roundtable, drawing swift controversy and an immediate public apology. He maintained, however, that the governments deserved credit as the only parties willing to underwrite Chrysler's recovery.
Fiat's stake in Chrysler steadily increased, and on 1 August 2014 the two companies formally merged into Fiat Chrysler Automobiles (FCA), then the seventh-largest automobile manufacturer in the world. Marchionne served as CEO of FCA and as chairman and CEO of FCA US LLC.
As chairman and CEO of Ferrari, Marchionne oversaw the Scuderia during one of its most turbulent and then resurgent competitive periods in Formula One. He combined commercial ambition with an uncompromising demand for results, famously setting public expectations for championship victories and holding Ferrari's leadership accountable in a manner that mirrored his wider management philosophy.
His 2015 presentation Confessions of a Capital Junkie, delivered to investors and analysts, argued forcefully for consolidation across the global automotive industry, citing the unsustainable capital expenditure required to develop next-generation powertrains. The presentation became widely read and debated across the industry.
Marchionne was also chairman of Maserati and chairman of the board of CNH Industrial, completing a portfolio that made him one of the most powerful figures in Italian industrial life.
Marchionne was known for a blunt, results-driven leadership style that blended North American directness with deep Italian industrial knowledge. He became recognizable for wearing black sweaters and jeans rather than the suits conventional in European boardrooms — a deliberate rejection of corporate formality that he maintained through decades of leadership. He was famously photographed wearing a necktie just once after 2007, on 1 June 2018, to mark FCA's final debt repayment.
His management approach involved radical flattening of corporate hierarchies and direct accountability. An analyst commented in 2009 that Marchionne was "quite ruthless" about replacing underperforming leadership but equally effective at clearing communication blockages that had allowed Fiat's problems to compound.
Marchionne's last public appearance came on 26 June 2018, when he presented a Jeep to the Italian Carabinieri in Rome. He then underwent shoulder surgery at the University Hospital of Zürich; complications from the procedure, related to an underlying illness he had kept largely private, proved fatal. On 21 July 2018, he resigned from all positions, and he died on 25 July 2018 at the age of 66.
He was survived by his partner Manuela Battezzato and his two adult sons, Alessio and Tyler.
In 2019, he was posthumously awarded the World Car Person of the Year at the Geneva Motor Show and inducted into the Automotive Hall of Fame. The Istituto Sergio Marchionne high school in Amatrice, rebuilt after the 2016 Central Italy earthquake and financed largely by the sale of the 500th LaFerrari, was opened in November 2019 in his memory. The American business channel CNBC described him as a "legend" of the automotive industry; the Financial Times called him "one of the boldest business leaders of his generation."
He held the Cavaliere del Lavoro, Italy's highest honour for business distinction, awarded in 2006.