Black Monday occurred on 19 October 1987, when the Dow Jones Industrial Average plunged 22.6% in a single trading session.
The fall was the largest one-day percentage decline in the Dow’s history. Stock markets in other countries also dropped sharply, making the event a genuinely international crash rather than an isolated American sell-off. Hong Kong, London, Australia and Canada were among the markets hit during the same episode.
Several forces contributed, including rising interest rates, overvalued shares, investor anxiety and widespread use of computerised program trading. Portfolio insurance strategies could automatically sell as prices fell, intensifying the downward movement. The crash did not develop into a depression like the 1929 collapse, partly because central banks supplied liquidity and financial institutions continued operating.
Black Monday is sometimes confused with Black Tuesday in 1929, but the two crashes occurred nearly six decades apart and had different economic consequences.