Black Monday is the name given to the global stock-market collapse that began on October 19, 1987.
On that day, the Dow Jones Industrial Average fell 22.6 percent, its largest one-day percentage decline. The selling spread rapidly to other markets, including those in London, Hong Kong, Australia, and Canada. Unlike the 1929 crash, the 1987 event did not lead to a decade-long depression, although it caused intense concern about financial stability.
Several factors were discussed afterward, including high valuations, rising interest rates, trade tensions, portfolio insurance, and computerized trading strategies. No single cause has been universally accepted. The Federal Reserve, led by Alan Greenspan, issued a statement supporting market liquidity, while exchanges later strengthened circuit breakers and other safeguards. The term Black Monday is also used for other market disasters, so the date and 1987 context identify this particular event.