The 1987 worldwide stock-market crash that began with a record Dow decline is known as Black Monday.
Black Monday refers primarily to 19 October 1987, when the Dow Jones Industrial Average fell 22.6 percent, its largest one-day percentage loss. Markets in other countries also plunged, making the event international rather than solely American. The decline followed a long rise in share prices and occurred amid worries about interest rates, trade imbalances, economic growth, and market valuations.
Computerized portfolio insurance and other program-trading strategies were widely examined because they could reinforce selling when prices fell. Regulators later introduced circuit breakers and other mechanisms intended to slow trading during extreme moves. Black Monday is not the same as the 1929 crash: that earlier episode is associated with Black Tuesday and a prolonged economic depression, while 1987 was followed by a relatively limited economic downturn in the United States. The shared weekday nickname is the main source of confusion.