The Monday of the 1987 global stock-market crash was called Black Monday.
On October 19, 1987, the Dow Jones Industrial Average fell 508 points, or 22.6 percent, in its largest one-day percentage decline. Markets in other countries also dropped sharply, making the event an international crash rather than a problem confined to the United States.
Several factors were associated with the fall, including overvalued markets, rising interest rates, trade tensions, and automated portfolio-insurance selling. The exact combination remains debated, but computerized trading accelerated the selling once prices began to slide.
Black Monday is often confused with the 1929 market episode, which also has trading days named Black Monday and Black Tuesday. In modern financial writing, “Black Monday” most commonly refers to October 19, 1987, unless another year is specified.