Lehman Brothers files for Chapter 11 bankruptcy, the largest bankruptcy filing in U.S. history.

Lehman Brothers Inc. 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, with about 25,000 employees worldwide. It was doing business in investment banking, equity, fixed-income and derivatives sales and trading, research, investment management, private equity, and private banking. Lehman was operational for 158 years from its founding in 1850 until 2008.

Chapter 11 of the United States Bankruptcy Code permits reorganization under the bankruptcy laws of the United States. Such reorganization, known as Chapter 11 bankruptcy, is available to every business, whether organized as a corporation, partnership or sole proprietorship, and to individuals, although it is most prominently used by corporate entities. In contrast, Chapter 7 governs the process of a liquidation bankruptcy, though liquidation may also occur under Chapter 11; while Chapter 13 provides a reorganization process for the majority of private individuals.

The bankruptcy of Lehman Brothers, also known as the Crash of '08 and the Lehman Shock, on September 15, 2008, was the climax of the subprime mortgage crisis. After the financial services firm was notified of a pending credit downgrade due to its heavy position in subprime mortgages, the Federal Reserve summoned several banks to negotiate financing for its reorganization. These discussions failed, and Lehman filed a Chapter 11 petition that remains the largest bankruptcy filing in U.S. history, involving more than US$600 billion in assets.