The 1987 worldwide stock-market crash is known as Black Monday because its most dramatic session occurred on Monday, October 19, 1987. The Dow Jones Industrial Average fell 22.6 percent in one day, the largest one-day percentage decline in its history.
Selling spread rapidly across international markets. Hong Kong fell first in the sequence of major market declines, followed by markets in Europe and the United States. Concerns about overvaluation, interest rates, trade tensions, and automated portfolio-insurance strategies all contributed to the turmoil.
The crash did not produce a depression like the one associated with 1929. Central banks supplied liquidity, and the U.S. Federal Reserve said it would serve as a source of liquidity to support the financial system. Markets eventually recovered, although the episode changed thinking about market structure and systemic risk.
Black Monday is sometimes confused with the 1929 Black Tuesday. They are separate crashes: Black Tuesday occurred on October 29, 1929, while Black Monday occurred on October 19, 1987.