Bill Ackman

William Albert Ackman (born May 11, 1966) is an American billionaire hedge fund manager who is the founder and chief executive of Pershing Square Capital Management, an investment management company. He has been described as an activist investor. As of April 2026, Ackman's net worth was estimated at $8 billion by Bloomberg.

A long-time donor to Democratic candidates and organizations, Ackman endorsed Donald Trump in the 2024 United States presidential election. Ackman has been an active supporter of Israel, particularly following the October 7 attacks, and has criticized the 2024 pro-Palestinian protests on university campuses.

Ackman was raised in Chappaqua, New York, the son of Ronnie I. (née Posner) and Lawrence David Ackman, the former chairman of a New York real estate financing firm, Ackman-Ziff Real Estate Group. He is of Ashkenazi Jewish descent.

He graduated from Horace Greeley High School in 1985. After high school, he graduated from Harvard College with a Bachelor of Arts, magna cum laude, in social studies in 1988. As an undergraduate, he wrote a senior thesis titled, "Scaling the Ivy Wall: The Jewish and Asian American Experience in Harvard Admissions". In 1992, he earned a Master of Business Administration (MBA) degree from Harvard Business School.

In 1992, Ackman founded the investment firm Gotham Partners with fellow Harvard graduate David P. Berkowitz. The firm made small investments in public companies. In 1995, Ackman partnered with the insurance and real estate firm Leucadia National to bid for Rockefeller Center. Although they did not win the deal, the bid generated interest in Gotham from investors, and three years later, Gotham had $500 million in assets under management (AUM). By 2002, Gotham had become entrenched in litigation with various external shareholders who also owned an interest in the companies in which Gotham invested.

In 2002, Ackman researched MBIA in order to challenge Standard & Poor's AAA rating of its bonds. At a billed cost of more than $100,000, his law firm copied 725,000 pages of statements regarding the financial services company to comply with a subpoena. Ackman called for a division between MBIA's structured finance business and its municipal bond insurance business.

He argued that MBIA was legally restricted from trading billions of dollars of credit default swap protection that it had sold against various mortgage-backed collateralized debt obligations, and was using a second corporation, LaCrosse Financial Products, which MBIA described as an "orphaned transformer." Ackman bought credit default swaps against MBIA corporate debt and sold them for a large profit during the 2008 financial crisis. He reported covering his short position on MBIA on January 16, 2009, according to the 13D filed with the United States Securities and Exchange Commission.

In 2003, a feud developed between Ackman and Carl Icahn over an investment deal. Ackman sued Icahn for his share of profits in a stock sale. In 2011, Icahn was forced to pay the $4.5 million plus 10% interest per year and legal fees, totaling $9 million.

In 2004, with $54 million from his personal funds and from his former business partner Leucadia National, Ackman started Pershing Square Capital Management.

Ackman has said that his most successful investments have always been controversial, and that his first rule of activist investing is to "make a bold call that nobody believes in." But he also values investment stability in a style of Warren Buffett, as reflected in his development of "permanent capital" and strategic corporate structuring with conglomerates like Howard Hughes Holdings.

His most notable market plays include shorting MBIA's bonds during the 2008 financial crisis, his proxy fight with Canadian Pacific Railway, and his stakes in the Target Corporation, Valeant Pharmaceuticals, and Chipotle Mexican Grill. From 2012 to 2018, Ackman held a US$1 billion short against the nutrition company Herbalife, a company he has described as a pyramid scheme designed as a multi-level marketing firm. His efforts were reported in the documentary film "Betting on Zero".

After weak performance in 2015–2018, Ackman reworked his management of Pershing Square. The next year, Pershing Square returned 58.1%, which Reuters says qualified it as "one of the world's best performing hedge funds" for 2019.

Critics of Ackman have called him an oligarch, basing accusations on his use of market manipulation and use of his wealth to push for his own policy preferences, particularly with respect to Israel.

Ackman is a signer of The Giving Pledge, committing to give away at least 50 percent of his wealth by the end of his life to charitable causes. In 2006, Ackman, and his then wife Karen, founded the Pershing Square Foundation to fund innovative organizations focused on economic development, education, healthcare, human rights, arts and urban development and more. Since its inception, the foundation has committed more than $750 million in grants to more than 100 organizations. Grantees have included One Acre Fund, Saïd Business School's Oxford-Pershing Square Graduate Scholarships, Cold Spring Harbor Laboratory, Center for Jewish History, Innocence Project, African Parks and Planned Parenthood. Ackman and his wife, Neri Oxman, are the Foundation's co-trustees as of 2024. In 2011, Bill and Karen Ackman were on The Chronicle of Philanthropy's "Philanthropy 50" list of the most generous donors; Ackman was listed again in 2021 with Neri Oxman.

On March 15, 2021, he announced that he donated 26.5 million shares (valued at $1.36 billion) in American e-commerce company Coupang to three entities, one of them his own foundation. Coupang, while based in the US, primarily operates in South Korea.

In December 2022, Ackman auctioned a lunch with himself for charity in partnership with the David Lynch Foundation. The proceeds would go toward helping "New York's frontline healthcare workers, police and veterans who battle anxiety, depression, addiction and suicide every day", with Ackman matching the winning bid to support the foundation. The highest winning bid over prior instances was $210,000.

Ackman is a supporter of David M. Sabatini, a biologist who was previously fired by the Howard Hughes Medical Institute and resigned from the Whitehead Institute and MIT due to allegations and investigations of sexual misconduct. On March 1, 2022, at a Pershing Square Foundation event, he delivered remarks about what he called Sabatini's unfair treatment. In February 2023, Ackman announced that his foundation and an anonymous donor would together fund Sabatini US$25 million over five years to establish and run a new research laboratory.

Following the Bondi Beach shooting in December 2025, Ackman promoted a GoFundMe page raising funds for Ahmed Al-Ahmed, known for famously disarming one of the attackers. Al-Ahmed is a Muslim migrant of Syrian descent. Ackman later donated $99,999 to the campaign.

Bill Ackman has expressed support for Israel's actions in the Gaza war and signed a pledge "not to hire students who participate in demonstrations against Israel."

On October 8, 2023, following the October 7 attacks, several Harvard undergraduate student groups signed a letter holding Israel "entirely responsible" for the War in Gaza, blamed Israeli apartheid for the war, and said Israel's blockade turned Gaza into an "open-air prison". The letter called on Harvard to "take action to stop the ongoing annihilation of Palestinians." In response, Ackman demanded the publication of the names of all students involved in signing the letter so that he could ensure his company and others do not "inadvertently hire" any of the signatories. Former Harvard president Lawrence Summers said Ackman's request for a list of names constituted McCarthyism.

Ackman was a member of a long-standing WhatsApp group chat with Israeli military leaders and top US business leaders with the stated goal to "change the narrative" in favor of Israel by conveying "the atrocities committed by Hamas" and "help [Israel] win the war" on U.S. public opinion following U.S. protests against the Gaza war. Group members, including Ackman, worked with the Israeli government to screen a film titled "Bearing Witness to the October 7th Massacre", which shows footage compiled by the Israel Defense Forces portraying killings committed by Hamas on October 7. Screenings of the film were conducted in New York City and, with Ackman's help, at Harvard University, his alma mater.

In November 2023, Ackman supported Elon Musk after he expressed support for antisemitic remarks made by an X user who falsely asserted that "Jewish communities" supported "hordes of minorities flooding their country" and pushed "dialectical hatred against whites", describing it as "shoot from the hip commentary".

The same month, Ackman engaged in a campaign to remove Claudine Gay from her position as Harvard's president. He argued that her response to antisemitism was "insufficient" and amplified allegations that she engaged in plagiarism. After Gay resigned in January 2024, Ackman called for the resignation of Senior Fellow of the Harvard Corporation Penny Pritzker and other members of the board on Twitter, and described the university's diversity, equity, and inclusion movement as the "root cause of antisemitism at Harvard" and "racism against white people".

Ackman married Karen Ann Herskovitz, a landscape architect, on July 10, 1994. They have three children. On December 22, 2016, it was reported that the couple had separated.

In 2018, Ackman became engaged to Israeli-American designer Neri Oxman. In January 2019, Oxman and Ackman married at the Central Synagogue in Manhattan, and they had their first child together in spring 2019. In August 2019, Ackman wrote to MIT Media Lab director Joi Ito to discourage him from mentioning Oxman when discussing convicted sex offender Jeffrey Epstein, who had donated $125,000 to Oxman's lab.