The market crash that began on October 19, 1987, in Hong Kong before spreading across global exchanges was Black Monday.
Hong Kong's Hang Seng Index fell sharply on October 19, and the selling then moved westward through international markets. European exchanges suffered heavy losses, followed by the United States, where the Dow Jones Industrial Average recorded its largest one-day percentage decline. The time-zone sequence helped create the impression of a crash moving around the world.
Black Monday is therefore a global event, not only an American one. Markets in Australia, the United Kingdom, Canada, and other economies were affected. The scale of the losses prompted central banks and regulators to examine market structure, derivatives, automated trading, and mechanisms for slowing extreme declines.
The name can cause confusion because “Black Monday” has also been used for other financial or political events. In stock-market history, the unqualified term usually refers to October 19, 1987, while the Hong Kong opening is an important part of the event's chronology.