The severe U.S. stock-market collapse on October 19, 1987, was known as Black Monday.
On that date, the Dow Jones Industrial Average fell 508 points, a decline of 22.6 percent in a single session. By percentage, it remains the largest one-day percentage fall in the Dow’s history. Stock markets in other countries also suffered substantial losses, making the event a global crash rather than only a U.S. episode.
Several factors were discussed afterward, including rapidly rising prices, concerns about trade and interest rates, and computerized portfolio-insurance strategies that automatically sold futures as prices fell. The precise balance among these causes remains debated, but the scale and speed of the selling were unmistakable.
The phrase Black Monday can also describe other market disasters, including October 28, 1929, in the United States. In a stock-market-crash context, however, the unqualified date October 19, 1987, identifies the most famous Black Monday.