The U.S. stock-market crash that began on October 19, 1987, after the Dow fell 22.6 percent was called Black Monday.
The one-day decline was the largest percentage fall in the Dow’s history. Selling spread rapidly through international markets, making the event a global crash rather than an isolated U.S. disturbance. Concerns about valuations, trade tensions, interest rates, and market structure all influenced the environment.
Computerized portfolio insurance and program trading were also examined as factors that may have accelerated selling. The exact contribution of each cause remains debated, but the episode led exchanges and regulators to reconsider trading safeguards.
This question uses the standard name of the event, not a general description of a market panic. “Black Tuesday” is associated with October 29, 1929, while “Black Thursday” is commonly associated with October 24, 1929. Those labels belong to the 1929 crash.