Lehman Brothers' September 2008 bankruptcy became the best-known trigger of the global financial crash.
Lehman Brothers filed for Chapter 11 bankruptcy protection on September 15, 2008, after suffering enormous losses linked to U.S. mortgages and related securities. With assets of about $639 billion, it was the largest bankruptcy filing in U.S. history at the time.
The failure intensified fears that other financial institutions could collapse because banks were deeply connected through loans, derivatives, and short-term funding markets. Credit markets seized up, stock markets fell sharply, and governments responded with emergency rescues, guarantees, and monetary measures.
The crisis had begun before Lehman's failure. The U.S. housing bubble had burst, subprime mortgage defaults had risen, and institutions had accumulated complex mortgage-related exposures. Lehman is therefore best understood as a dramatic accelerant and symbol of the crisis, not its sole underlying cause.