Black Monday, the 1987 stock-market crash, occurred on October 19, 1987, when the Dow Jones Industrial Average lost 22.6% in one trading session.
The fall was the largest one-day percentage decline in the Dow's history. Selling spread rapidly through major markets, including Hong Kong, London, and Australia, making the event an unusually international crash rather than an isolated Wall Street panic.
Several forces contributed, including anxiety about interest rates, overvalued shares, program trading, and portfolio-insurance strategies. These automated and rules-based systems could intensify selling once prices began to fall. The crash did not develop into a depression like the 1929 collapse, and the U.S. economy continued expanding afterward.
A common mix-up is confusing Black Monday with the 1929 day often called Black Tuesday. Black Monday refers specifically to the 1987 global equity-market shock.