What was the famous name of the U.S. stock-market collapse that began in October 1929?

The famous U.S. stock-market collapse that began in October 1929 was the Wall Street Crash of 1929.

Share prices had risen dramatically during the 1920s, supported by speculation and widespread purchases made with borrowed money. In October, selling accelerated as investors lost confidence. The most remembered trading days were Black Thursday on 24 October, Black Monday on 28 October, and Black Tuesday on 29 October.

The crash did not by itself cause every feature of the Great Depression, but it severely damaged confidence and reduced household and business wealth. Bank failures, falling production, deflation, and unemployment followed through the early 1930s.

The crash is often used interchangeably with the start of the Great Depression, although the depression was a longer economic crisis with additional causes. The Dow Jones Industrial Average did not regain its 1929 peak until 1954.