Jacob Ezra Merkin (born April 19, 1953) is an American investor, hedge fund manager and philanthropist. He had been a fund manager and capital raiser until 2008 when one of the funds in Gabriel Capital LP, his $5 billion group of hedge funds became insolvent because a large portion of its assets was invested with the convicted Ponzi scheme operator Bernard Madoff. The fallout from his investment with Madoff has been extensive. He navigated a series of lawsuits without a finding of fraud or knowledge of the scheme, but agreed to repay any fees earned from the investment in Madoff historically. He had to resign a series of positions including his role as non-executive chairman of GMAC.