The 1987 global stock-market crash whose largest one-day percentage fall occurred on October 19 was called Black Monday.
On that date, the Dow Jones Industrial Average fell 22.6 percent, the largest one-day percentage decline in its history. Markets in other countries also suffered severe losses, making the event international rather than limited to Wall Street.
Several forces contributed to the turmoil, including high valuations, worries about interest rates and trade deficits, portfolio insurance, and computerized selling strategies. Once prices began falling, automated and institutional orders added selling pressure and overwhelmed market liquidity.
Black Monday is distinct from Black Tuesday, the name commonly associated with October 29, 1929, during the earlier Wall Street Crash. The 1987 episode did not produce a depression on the scale of the 1930s, partly because central banks supplied liquidity and financial authorities worked to restore confidence.