The 1987 market crash that spread across stock exchanges worldwide was called Black Monday.
The name usually refers specifically to 19 October 1987, when the Dow Jones Industrial Average fell 22.6%. The crash was international: markets in Asia, Europe, and the Americas all experienced major losses around the same period. Because the most famous US fall occurred on a Monday, the event received its enduring nickname.
The rapid decline raised concerns about computerized trading, portfolio insurance, liquidity, and the ability of markets to absorb large orders. Policymakers responded with reforms, including circuit breakers and other procedures intended to slow trading during extreme volatility.
Black Monday is sometimes confused with the 1929 Black Tuesday episode because both names describe famous crashes and both involved the Dow. The crucial distinction is date: Black Monday belongs to 1987, while Black Tuesday belongs to 1929.