The severe 1987 global stock-market crash was nicknamed Black Monday because of the dramatic fall on October 19, 1987.
The Dow Jones Industrial Average dropped 22.6 percent that day, the largest one-day percentage decline in its history. Markets in other countries also fell sharply, creating a synchronized international shock rather than a crisis confined to one exchange.
Several factors contributed, including stretched valuations, rising interest rates, trade concerns, and computerized trading strategies. Portfolio insurance was designed to limit losses, but its selling rules could intensify downward momentum when prices dropped rapidly.
Black Monday did not produce a Great Depression-style economic collapse. Central banks supplied reassurance and liquidity, and new market safeguards were introduced. The New York Stock Exchange later developed circuit breakers intended to pause trading during exceptionally rapid declines. The nickname is distinct from Black Tuesday, the famous climax of the 1929 Wall Street Crash.