Lehman Brothers Inc. (/ˈliːmən/ LEE-mən) was an American global financial services firm founded in 1850. Before filing for bankruptcy in 2008, Lehman was the fourth-largest investment bank in the United States (behind Goldman Sachs, Morgan Stanley, and Merrill Lynch), with about 25,000 employees worldwide. It did business in investment banking, equity, fixed-income and derivatives sales and trading (especially U.S. Treasury securities), research, investment management, private equity, and private banking. Lehman was operational for 158 years from its founding in 1850 until 2008.
On September 15, 2008, Lehman Brothers filed for Chapter 11 bankruptcy protection following the exodus of most of its clients, drastic declines in its stock price, and the devaluation of assets by credit rating agencies. The collapse was largely due to Lehman's involvement in the subprime mortgage crisis and its exposure to less liquid assets. Lehman's bankruptcy filing is the largest in US history, having beaten the previous record holder Worldcom, Inc., and is thought to have played a major role in the unfolding of the 2008 financial crisis. The market collapse also gave support to the "too big to fail" doctrine.