The worldwide stock-market plunge on October 19, 1987, was commonly called Black Monday.
On that Monday, major markets fell sharply, beginning in Hong Kong and spreading through Europe and North America. The Dow Jones Industrial Average dropped 22.6%, its largest one-day percentage decline. Other indexes also recorded exceptionally large losses, making the event one of the most dramatic synchronized market shocks of the twentieth century.
The crash followed a period of strong gains and rising concern about valuation, interest rates, trade imbalances, and economic growth. Automated trading programs and portfolio insurance may have accelerated the sell-off by generating additional sell orders as prices fell.
Black Monday is sometimes confused with Black Tuesday, the major session of the 1929 Wall Street Crash. These names refer to different events: Black Monday was in 1987, while Black Tuesday was in 1929. Despite the scale of the decline, the 1987 crash did not lead to a prolonged depression.