Black Monday was the U.S. stock-market crash that began on October 19, 1987, when the Dow fell 22.6%.
The decline was part of a worldwide market shock. Asian and European exchanges had already fallen, and selling continued when Wall Street opened. The Dow’s 508-point drop was its largest one-day percentage loss, while the S&P 500 and other major indexes also recorded severe declines.
Analysts identify several contributing factors, including high valuations, rising interest rates, trade disputes, and investor fear. Program trading and portfolio insurance could automatically generate sell orders as prices declined, adding to the downward momentum. These mechanisms helped prompt later changes in trading rules and circuit breakers.
Black Monday did not lead to a depression comparable to the 1930s. Economic growth continued, and the market eventually recovered. The nickname can also cause confusion because “Black Monday” has been used for other market declines, but in stock-market history it most commonly refers to October 19, 1987.