The 1987 market crash that produced the largest one-day percentage falls on many stock exchanges was Black Monday.
Black Monday occurred on October 19, 1987. The Dow Jones Industrial Average dropped 22.6% in a single session, while major markets in the United Kingdom, Hong Kong, Australia, and elsewhere also recorded extraordinary losses.
The sell-off followed a sharp rise in share prices earlier in the decade. Explanations include overvaluation, economic concerns, currency tensions, and computer-driven portfolio insurance that could accelerate selling once prices began to fall.
The crash differed from 1929 because the financial system did not collapse into a comparable decade-long depression. Central banks supplied liquidity, trading rules were changed, and markets eventually recovered. Black Monday is distinct from the 1987 crash's later anniversary labels.