The Cornell graduate founded New York-based hedge fund Greenlight Capital Inc. in 1997 with $1 million under management. The firm has been highly successful, often by "shorting" the stocks of companies that have hidden weaknesses.
Einhorn took on financial firm Allied Capital in 2002, shorting its stock because he believed its assets were overvalued. The Securities and Exchange Commission found in 2007 that the company was breaking laws related to asset valuation, and the company succumbed during the 2008 credit crunch.
The highest-profile victim of the credit crunch was Lehman Brothers, which Einhorn shorted in 2007 because he believed it had large liabilities that were improperly accounted for.
More recently, his comments have sent the stock of Green Mountain Coffee Roasters, Herbalife and Chipotle Mexican Grill plummeting.
Last year, British regulators fined Einhorn and Greenlight Capital $11 million for trading on inside information from a Merrill Lynch director.
Einhorn is also a crack poker player. He finished 18th in the 2006 World Series of Poker. In 2012, he finished third in a tournament with a $1 million buy-in, and walked away with $4.35 million, according to the New York Times.
Forbes lists his wealth as of Sept. 2012 at $1.2 billion.