William Ackman

William Albert Ackman (born May 11, 1966) is an American hedge fund manager and activist investor who founded Pershing Square Capital Management, L.P. in 2003, serving as its CEO and portfolio manager. Educated at Harvard College, from which he graduated with a bachelor's degree in social studies in 1988, and Harvard Business School, where he earned an MBA in 1992, Ackman built his career through high-conviction, concentrated bets on public companies, often pushing for operational and governance reforms as an activist shareholder.

Ackman's investment record features outsized successes, such as his role in the restructuring of General Growth Properties during the 2008 financial crisis and value-unlocking changes at Canadian Pacific Railway, alongside concentrated positions in firms like Uber and Howard Hughes Holdings, but it has also included significant setbacks, including a multibillion-dollar writedown on Valeant Pharmaceuticals amid revelations of its aggressive pricing and distribution practices, and a $1 billion loss on a short position against Herbalife, which he publicly framed as exposing potential multi-level marketing risks despite the financial outcome. Pershing Square's performance rebounded strongly in subsequent years, with the main fund returning about 25% year-to-date as of September 2025, propelled by gains in holdings like Fannie Mae, Freddie Mac, and Amazon, elevating Ackman's net worth to approximately $9.2 billion.

William Albert Ackman was born on May 11, 1966, in Chappaqua, New York, to Lawrence David Ackman, chairman of Ackman-Ziff Real Estate Group, a New York real estate financing firm, and Ronnie I. Ackman (née Posner). He was raised in a Jewish family in the affluent hamlet of Chappaqua, located in Westchester County. There is no reliable evidence that Ackman received significant inheritance from his family; his wealth derives primarily from his own career, including co-founding Gotham Partners in 1992 and founding Pershing Square Capital Management in 2004 with $54 million in personal funds and backing from Leucadia National. Ackman attended Horace Greeley High School in Chappaqua, from which he graduated before gaining admission to Harvard College.

In late 2018, Ackman became engaged to Neri Oxman, an Israeli-born architect, designer, and former MIT professor known for her work in computational design and biomimicry. The pair married on January 19, 2019, at Central Synagogue in New York, officiated by Rabbi Angela Buchdahl. Their daughter was born later that year. Ackman has publicly credited his relationship with Oxman for providing personal stability during professional challenges, including the turnaround of his hedge fund Pershing Square Capital Management.