Black Tuesday was 29 October 1929, the New York Stock Exchange day associated with the climax of the Wall Street Crash.
Selling had already intensified on Black Thursday, 24 October, and Black Monday, 28 October. On 29 October, roughly 16 million shares changed hands as investors rushed to sell. The huge volume overwhelmed the market and deepened public fear.
The crash followed a speculative boom in American shares during the 1920s. Many investors bought stock with borrowed money, known as buying on margin. When prices fell, margin calls forced further selling, creating a damaging cycle.
The crash did not single-handedly cause the Great Depression, but it became its most famous financial symbol. Bank failures, reduced lending, falling production, and unemployment turned the market collapse into a much broader economic crisis. The 1929 episode is often confused with the entire Depression, which lasted for years afterward.