Bill Ackman grew up in Chappaqua, New York, in a real estate finance family, graduated magna cum laude from Harvard in 1988 with a thesis on Harvard admissions, and earned a Harvard MBA in 1992 before founding Gotham Partners. In 2002 he bet against bond insurer MBIA, arguing its AAA rating hid exposure to risky debt; his law firm copied 725,000 pages of financial statements, and he endured regulatory scrutiny until the 2008 crash proved him right. He launched Pershing Square Capital Management in 2004 with about $54 million and in 2011 won a proxy fight at Canadian Pacific Railway that replaced the CEO and board.

Losses followed at J.C. Penney and Valeant, where he lost nearly $4 billion. In 2012 he announced a $1 billion short against Herbalife, calling it a pyramid scheme, and Carl Icahn, his rival since a 2003 lawsuit, took the other side; Ackman exited at a loss in 2018. In March 2020 he warned on television that “hell is coming” while a $27 million credit hedge grew to $2.6 billion in under a month. After October 7, 2023 he demanded the names of Harvard students who signed a letter blaming Israel, campaigned against president Claudine Gay until she resigned in January 2024, and endorsed Donald Trump that year.

• Pershing Square runs about $35 billion with 48 employees, all given stock, and reportedly zero turnover.
• In 2021 Pershing Square took 10 percent of Universal Music Group, which owns a 1926 song written by his grandfather Herman Ackman.
• Lawrence Summers compared the demand to publish students’ names to McCarthyism.
• After plagiarism claims about his wife Neri Oxman’s dissertation, he vowed an AI review of MIT faculty.
• At 59 he played doubles at the 2025 Hall of Fame Open in Newport on a wild card, and the Hall declined his $10 million endowment offer.