The 1987 worldwide stock-market collapse is known as Black Monday.
Black Monday occurred on 19 October 1987. The Dow Jones Industrial Average fell 22.6 percent in a single session, its largest one-day percentage decline. Markets in Hong Kong, London, and other financial centers also plunged, showing how closely global trading had become connected.
Several forces contributed, including overvalued shares, rising interest rates, currency tensions, and computerized portfolio-insurance strategies that encouraged selling as prices dropped. The exact balance of causes remains debated, but the scale of synchronized selling is clear.
Black Monday was not followed by a depression comparable to the 1930s. Central banks supplied liquidity, and the U.S. economy continued expanding. Regulators later introduced circuit breakers designed to pause trading during extreme price movements.