Who is Bill Ackman — and why is this Donald Trump supporter now angry with him?

If you’ve been online—or anywhere near a financial screen—you've probably seen one word shaking global markets: TARIFF. It’s not just a buzzword anymore, it’s the thunderbolt that lit up what Donald Trump dubbed “Liberation Day.” Initially scheduled for April 1, the event was pushed to April 2 because, as Trump himself put it, “Nobody would believe what I said.” And frankly, it’s easy to see why.


On this rescheduled "Liberation Day," Trump dropped a tariff bombshell—announcing “reciprocal” tariffs that hit nearly every country in the world. A sweeping 10% baseline tax was slapped on all imports, with significantly steeper rates for countries with trade surpluses with the U.S.



Trump’s allies praised the President’s decision as a long-overdue correction to "unfair trade," while critics warned it could ignite a full-blown global economic crisis. But what turned heads wasn’t just the global fallout or the opposition from familiar political adversaries—it was the surprise dissent from within Trump’s own corner. One of his most prominent financial backers- William Ackman- has publicly urged him to pause this trade war before it spirals out of control.


What did William Ackman say?In a strongly worded post on X (formerly Twitter), Ackman urged Trump to pause the economic aggression before things spiral further out of control. “The President has an opportunity to call a 90-day time out,” Ackman said, encouraging negotiation over escalation.

His warning comes amid intense market turmoil triggered by Trump’s sweeping new tariffs. Last week alone, U.S. markets saw a staggering $2 trillion loss in value, with futures continuing to trend downward. Ackman didn’t mince words about the gravity of the situation, especially when it comes to Trump’s standing among the very people who once championed him.

To state the obvious, it does not help our country’s and our president’s negotiating position to be trying to strike deals while our market is collapsing.

Whoever is recommending that idea to President @realDonaldTrump should be fired now.

— Bill Ackman (@BillAckman) April 6, 2025

“Business is a confidence game. The president is losing the confidence of business leaders around the globe,” he wrote. “The consequences for our country and the millions of our citizens who have supported the president — in particular low-income consumers who are already under a huge amount of economic stress — are going to be severely negative,” said Ackman

He also added, “This is not what we voted for.”

Ackman’s bluntest caution came near the end of his post, warning of an economic freeze if the administration doesn’t pivot soon: “If we start an economic nuclear war, business investment stops and consumer spending dries up overnight.”

Meet William Ackman—the billionaire who has dared to oppose Trump’s decision
William Albert Ackman, better known as Bill Ackman , is one of Wall Street’s most recognized faces. Born on May 11, 1966, Ackman grew up in the upscale suburb of Chappaqua, New York, the son of Ronnie, a homemaker, and Lawrence, a real estate mortgage broker. He attended Horace Greeley High School, then went on to Harvard University, where he rowed crew, majored in history, and graduated Magna Cum Laude in 1988.

After two years in his father’s real estate firm, Ackman returned to Harvard Business School, where he earned his MBA in 1992. That same ambition drove him to co-found Gotham Partners, his first hedge fund, followed by Pershing Square Capital Management in 2003—now the cornerstone of his financial empire.


According to Bloomberg, Ackman is credited with a 45% stake in Pershing Square, which managed around $19 billion in assets as of late 2024

Beyond the fund, Ackman also controls an estimated $2.25 billion through his family office, Table Management, and owns about 41.4 million shares in Pershing Square’s publicly traded closed-end fund.

About his personal life, Ackman is a father of four children and has been married twice. His first marriage to landscape architect Karen Ann Herskovitz ended in 2016. In 2019, he tied the knot with Neri Oxman, an Israeli-American architect, designer, and MIT professor, in a ceremony at New York's Central Synagogue. The couple welcomed their first child the same year.