During the 1987 global stock-market crash, October 19, 1987, was nicknamed Black Monday.
On that day, the Dow Jones Industrial Average fell 22.6 percent, the largest one-day percentage decline in its history. Selling spread rapidly from Hong Kong and other Asian markets to Europe and North America. Modern electronic trading and portfolio-insurance strategies intensified the speed of the decline.
The fall was dramatic, but it did not produce a depression comparable to the 1930s. Central banks supplied liquidity, and the Federal Reserve under Alan Greenspan publicly signaled that it was prepared to support the financial system. Markets eventually recovered, although the crash led regulators to examine trading safeguards.
Black Monday is sometimes confused with the Black Monday of 1929 or with later market sell-offs that used the same nickname. In the 1987 context, the term specifically refers to October 19 and the worldwide crash associated with it.