The 1987 global stock-market collapse that began in Hong Kong before spreading westward was called Black Monday.
The crisis unfolded across several time zones. Hong Kong’s market fell sharply on October 19, 1987, and selling then reached Europe and the United States. The Dow Jones Industrial Average dropped 22.6 percent on October 19, its largest one-day percentage decline in its history.
Concerns included high valuations, rising interest rates, trade tensions, and the growing use of computerized portfolio insurance. That strategy could generate additional selling when prices fell, although historians and economists debate the relative importance of each cause.
Central banks responded with liquidity and reassurance. The crash did not produce a depression like the 1929 collapse, and US markets recovered over time. “Black Monday” can also refer to October 28, 1929, so the year and the 1987 global sequence are important for identifying this event.