The October 1987 market crash known as the largest one-day percentage fall in Dow history was Black Monday.
Black Monday took place on October 19, 1987. The Dow Jones Industrial Average fell 22.6%, a decline larger in percentage terms than any other single day in the index’s history. Selling was international: markets in Hong Kong, Australia, Britain, and other financial centers also suffered severe losses.
The collapse followed a period of strong price increases and growing concern about interest rates, currency values, trade tensions, and economic conditions. Computerized trading strategies helped accelerate selling once prices began to fall. Central banks and financial institutions supplied reassurance and liquidity, helping prevent the crash from becoming a 1930s-style depression. “Black Monday” can refer to other market episodes, including one in 1929, so the year is essential when identifying this specific crash.