What nickname is commonly given to the worldwide stock-market collapse that began in October 1929?

The worldwide stock-market collapse that began in October 1929 is commonly called the Wall Street Crash of 1929.

The crash followed a period of heavy speculation in American shares, widespread buying on margin, and rapid growth in stock prices during the 1920s. Prices began falling sharply in October, with especially severe selling on October 24, October 28, and October 29. The New York Stock Exchange was the main symbolic center, but the economic effects spread internationally.

The crash did not by itself cause every feature of the Great Depression, but it deepened financial uncertainty, reduced wealth, weakened banks and businesses, and contributed to falling investment and employment. A common mix-up is treating the crash and the Great Depression as identical events: the crash was a market event, while the depression was a much broader and longer economic crisis.

The crash also encouraged later reforms in securities regulation and market supervision in the United States.