Lehman Brothers failed in September 2008, becoming a defining event of the global financial crisis.
The investment bank filed for Chapter 11 bankruptcy on September 15, 2008. It was the largest bankruptcy filing in U.S. history at that time, with enormous assets and liabilities tied to mortgages, securities, and other financial contracts.
Lehman had been heavily exposed to the U.S. housing downturn and mortgage-related securities. Its failure intensified distrust among financial institutions, disrupted credit markets, and contributed to a sharp worldwide fall in stock prices.
Bear Stearns had already collapsed into a rescue sale in March 2008, while Merrill Lynch was acquired by Bank of America in September. Those events are related, but they were not the Lehman bankruptcy itself.