Black Monday was the 1987 crash widely recognized as the first major worldwide stock-market collapse intensified by computerized trading.
On October 19, 1987, markets fell sharply across Asia, Europe, and North America. The Dow Jones Industrial Average dropped 508 points, or 22.6%, its largest one-day percentage loss. Portfolio insurance programs automatically sold futures as markets declined, adding to downward pressure.
Computerized trading did not create all the conditions behind the crash. Investors were also concerned about valuations, interest rates, the U.S. dollar, and international trade tensions. The interaction between automatic selling and a market already under stress made the decline unusually rapid.
The event led regulators and exchanges to develop coordinated trading halts, commonly called circuit breakers. Black Monday is distinct from the 1929 Black Tuesday crash and from the 1987 market declines that occurred on other days around the world.