The worldwide stock-market crash of October 19, 1987, was widely nicknamed Black Monday.
The name describes the date on which several major markets suffered extraordinary losses. Hong Kong's market fell first, European exchanges followed, and the U.S. Dow Jones Industrial Average then recorded its historic 22.6% one-day percentage decline. Because time zones separated the markets, the same episode appeared on different calendar dates in some countries.
Black Monday is sometimes confused with other market “Black” days, especially Black Thursday in 1929 and Black Tuesday in the United States. Those labels refer to separate episodes. Black Monday specifically identifies the coordinated global sell-off in 1987.
The crash prompted investigations into market structure and automated trading. Regulators concluded that modern trading systems could amplify fear when many sell orders arrived together. Exchanges subsequently adopted coordinated trading halts and other safeguards. Despite the severity of the one-day fall, the crash did not produce the same prolonged economic collapse associated with the Great Depression.