What name is given to the rapid US stock-market collapse of October 1987?

The rapid US stock-market collapse of October 1987 is called Black Monday.

Black Monday refers specifically to October 19, 1987, when the Dow Jones Industrial Average lost 22.6% of its value. The decline followed steep falls in markets including Hong Kong, London, and Australia, making the episode an international crash rather than an isolated US event.

Several factors were blamed, including computerized program trading, portfolio-insurance strategies, high share valuations, trade tensions, and investor psychology. Markets recovered partly after central banks and financial institutions reassured investors about liquidity.

The name can cause confusion because Black Tuesday usually refers to October 29, 1929, while Black Thursday is commonly associated with October 24, 1929. The 1987 crash did not lead to a depression comparable to the 1930s downturn.