William Albert Ackman, commonly known as Bill Ackman, is an American billionaire hedge fund manager and activist investor, and the founder and CEO of Pershing Square Capital Management. Born on May 11, 1966, in Chappaqua, New York, he was raised in an affluent Ashkenazi Jewish family as the son of real estate developer Lawrence David Ackman, former chairman of the Ackman-Ziff Real Estate Group, and Ronnie I. Ackman (née Posner). Ackman graduated from Horace Greeley High School in 1985 before attending Harvard College, where he earned a Bachelor of Arts degree magna cum laude in social studies in 1988; his undergraduate thesis examined Jewish and Asian American experiences in Harvard admissions. He later obtained a Master of Business Administration from Harvard Business School in 1992. His early career included real estate investment banking at Ackman Brothers & Singer, Inc., co-founding Gotham Partners Management in the 1990s, and launching Pershing Square Capital Management in 2003, where he serves as CEO and portfolio manager, focusing on concentrated, research-intensive investments and activist campaigns for corporate change. He is considered a fellow activist hedge fund manager and has a longtime rivalry with some peers in the field. Ackman has achieved notable successes, such as aiding the restructuring of General Growth Properties during the 2008 financial crisis and reforms at Canadian Pacific Railway, though he faced high-profile setbacks like his multi-year short against Herbalife, which he ultimately abandoned. As of July 2025, his net worth is estimated at $9.4 billion by Forbes. He has held board positions including Chairman of Howard Hughes Holdings and memberships on the Federal Reserve Bank of New York's Investor Advisory Committee and Harvard Business School's Board of Dean’s Advisors. In philanthropy, he co-founded the Pershing Square Foundation in 2006 and is a major donor to the University of Pennsylvania. Politically, a long-time Democratic donor, Ackman endorsed Donald Trump in the 2024 election and has been vocal in support of Israel, criticizing university responses to pro-Palestinian protests. He led a public campaign demanding the resignation of university presidents over their handling of antisemitism, successfully pressuring out Harvard President Claudine Gay, who resigned in January 2024 amid plagiarism allegations he amplified, and University of Pennsylvania President Liz Magill. Ackman was married to Karen Herskovitz from 1994 to 2018, with whom he has four children, and married Neri Oxman in 2019. He maintains an active presence on social media, particularly X (formerly Twitter) under @BillAckman, where he shares views on markets, politics, and current events. Known for collaborations like with Paul Singer early in his career, Ackman exemplifies high-conviction investing with influence across finance, academia, and public discourse.