Black Tuesday was the nickname for 29 October 1929, when the Dow Jones Industrial Average fell about 12% during the Wall Street Crash.
The session followed Black Thursday on 24 October and a temporary recovery attempt over the next few trading days. Heavy selling, panicked investors, and forced liquidation pushed millions of shares onto the market. The Dow continued falling after 29 October and did not reach its eventual low until July 1932.
The crash followed a period of rapid speculation and widespread use of borrowed money to buy shares. It was a major financial shock, but historians generally describe the Great Depression as resulting from several interacting causes, including banking failures, monetary contraction, and collapsing demand.
Black Tuesday is not the same event as Black Monday in 1987, which produced a larger one-day percentage fall in the Dow.