Bill Ackman

Origins and early life

William Albert Ackman was born in Chappaqua, New York, in 1966 to Ronnie Posner and Lawrence Ackman, a real-estate financier, in an Ashkenazi Jewish family. "I was raised in the Reform movement, so not particularly religious," he has said, "but I also raised my kids Jewish." He took a degree in social studies at Harvard in 1988 and an MBA there in 1992, founded Gotham Partners the same year with David Berkowitz, and in 2004 Pershing Square Capital Management with fifty-four million dollars.

Work and career

He is an activist investor: he buys a large stake in a company, then argues in public for the changes he wants. He began studying the bond insurer MBIA in 2002 and bet against it for years before the 2008 crisis proved him right; he took the board of Canadian Pacific in 2012; he lost heavily on a five-year public short against Herbalife, closed in 2018; and in March 2020, having bought twenty-seven million dollars of credit protection as the pandemic began, he made two point six billion in a month.

Bloomberg put his fortune at about eight billion dollars in April 2026. With Karen Ackman he founded the Pershing Square Foundation in 2006, which has committed more than seven hundred and fifty million dollars to over a hundred organisations — the One Acre Fund, the Innocence Project and Cold Spring Harbor Laboratory among them — and he has signed the Giving Pledge, promising away at least half his wealth. His family endowed the Ackman-Ziff Family Genealogy Institute at the Center for Jewish History in 2007, the first permanent Jewish genealogy centre in the United States open to the public; in December 2025 he and Neri Oxman pledged the Center twenty-five million dollars, on condition that it raise as much again.

After 7 October 2023 he became one of the most visible voices in America against antisemitism on university campuses: from 8 October he asked Harvard to publish the names of the students who had signed a letter holding Israel responsible, so that employers would not hire them, and he led the campaign that ended with the resignation of the university's president in January 2024. Both the demand and the campaign were sharply contested.