The Wall Street Crash of 1929, also known as the Great Crash, was a major American stock market crash that occurred in the autumn of 1929. It started in September and ended late in October, when share prices on the New York Stock Exchange collapsed.

It was the most devastating stock market crash in the history of the United States, when taking into consideration the full extent and duration of its aftereffects. The Great Crash is mostly associated with October 24, 1929, called Black Thursday, the day of the largest sell-off of shares in U.S. history, and October 29, 1929, called Black Tuesday, when investors traded some 16 million shares on the New York Stock Exchange in a single day. The crash, which followed the London Stock Exchange's crash of September, signaled the beginning of the Great Depression.

The New York Stock Exchange (NYSE, nicknamed "The Big Board") is an American stock exchange in the Financial District of Lower Manhattan in New York City. It is by far the world's largest stock exchange by market capitalization of its listed companies at US$30.1 trillion as of February 2018. The average daily trading value was approximately US$169 billion in 2013. The NYSE trading floor is at the New York Stock Exchange Building on 11 Wall Street and 18 Broad Street and is a National Historic Landmark. An additional trading room, at 30 Broad Street, was closed in February 2007.

The NYSE is owned by Intercontinental Exchange, an American holding company that it also lists (NYSE: ICE). Previously, it was part of NYSE Euronext (NYX), which was formed by the NYSE's 2007 merger with Euronext.