The Wall Street Crash of 1929, also known as the Great Crash or the Crash of '29, was a major American stock market crash that occurred in the autumn of 1929. It began in September, when share prices on the New York Stock Exchange (NYSE) collapsed, and ended in mid-November. The pivotal role of the 1920s' high-flying bull market and the subsequent catastrophic collapse of the NYSE in late 1929 is often highlighted in explanations of the causes of the worldwide Great Depression.

A stock market crash is a sudden dramatic decline of stock prices across a major cross-section of a stock market, resulting in a significant loss of paper wealth. Crashes are driven by panic selling and underlying economic factors. They often follow speculation and economic bubbles.