The worldwide stock-market plunge of 19 October 1987 is known as Black Monday.
On that Monday, the Dow Jones Industrial Average fell 22.6 percent, the largest one-day percentage decline in its history. Major markets in Australia, Hong Kong, the United Kingdom, and elsewhere also dropped sharply, making the event genuinely global rather than a solely American shock.
Several factors were blamed, including overvalued shares, rising interest rates, trade tensions, and computerized portfolio-insurance selling. The exact combination remains debated, but automated sell orders clearly accelerated the decline once prices began falling.
Unlike 1929, the 1987 crash did not produce a decade-long depression. Central banks supplied liquidity, companies continued operating, and the Dow eventually recovered its pre-crash level. The date is sometimes confused with Black Monday in 1929, which occurred on October 28.