In the global stock-market crash of 1987, the record one-day fall on October 19 is commonly called Black Monday.
The Dow Jones Industrial Average dropped 508 points, or 22.6 percent, in a single session. That percentage loss remains the largest one-day percentage decline in the Dow’s history, although the index had existed for many decades before 1987.
The sell-off spread rapidly across international markets. Hong Kong fell first in the crisis sequence, and sharp declines followed in Europe and the United States. Program trading, portfolio insurance, overvaluation concerns, and international monetary tensions were among the factors examined afterward.
Black Monday is distinct from the Black Monday of October 28, 1929. The shared nickname refers to the day of the week and the severity of each market collapse, not to one continuous event.