The severe global stock-market drop on October 19, 1987, was called Black Monday.
The Dow Jones Industrial Average fell 508 points, or 22.6%, in a single session. That percentage decline remains the largest one-day percentage fall in the Dow’s history. Markets in several other countries also suffered dramatic losses, making the event international rather than solely American.
Several factors were discussed afterward, including overvalued shares, rising interest rates, trade tensions, portfolio insurance, and computer-assisted trading. No single explanation completely accounts for the speed and scale of the selling. Modern market safeguards were partly developed in response to the episode.
Black Monday is sometimes confused with the 1929 crash dates, which also have weekday nicknames. The 1987 event was not the beginning of the Great Depression, and the economy recovered without a depression on the scale of the 1930s. The Dow returned to its pre-crash closing level by 1989.