The U.S. stock-market crash that began on October 19, 1987, with the Dow’s largest one-day percentage loss was Black Monday.
The Dow Jones Industrial Average fell 22.6 percent in that session, and declines spread rapidly to exchanges around the world. The event remains a central example of how market expectations and trading mechanisms can amplify selling.
Analysts identified several contributing conditions, including high valuations, interest-rate concerns, trade tensions, and computerized trading strategies. Investigations did not find one universally accepted cause.
Black Monday is sometimes confused with Black Tuesday of 1929. The names refer to different crashes: Black Monday was October 19, 1987, while Black Tuesday was October 29, 1929.