Black Monday, the 1987 stock-market crash when the Dow Jones Industrial Average fell 22.6%, occurred on October 19, 1987.
The Dow dropped 508 points in one trading session, then the largest one-day percentage decline in its history. Selling spread rapidly across international markets, including Hong Kong, London, and Australia, so the event became known as a global crash rather than only a U.S. market shock.
Several factors contributed, including overvalued shares, rising interest rates, trade tensions, and computerized portfolio-insurance strategies. Many historians and financial analysts still debate how much each factor mattered, but the date and the Dow's percentage loss are firmly established.
The crash also prompted major changes. U.S. exchanges introduced circuit breakers that can temporarily halt trading after sharp declines. Black Monday is often confused with the 1929 crash dates, but October 19, 1987, is specifically the defining date of the modern event.