Black Thursday was the first major panic day of the 1929 Wall Street Crash, occurring on October 24, 1929.
On Black Thursday, approximately 12.9 million shares changed hands on the New York Stock Exchange, at a time when that volume was extraordinary. Prices fell sharply after a period of heavy speculation and rising use of borrowed money to buy stocks. A group of major bankers then attempted to restore confidence by purchasing leading shares.
That intervention temporarily steadied the market, but it did not end the crisis. Selling returned on the following Monday and became even more severe on Black Tuesday, October 29. The crash unfolded alongside a broader economic contraction that became the Great Depression.
Black Thursday is sometimes used loosely for the entire 1929 crash, but the name specifically identifies October 24. Black Tuesday identifies October 29, the most famous collapse day of the episode.