What was the common name for the 29 October 1929 US stock-market collapse?

The 29 October 1929 US stock-market collapse was called Black Tuesday.

The name refers to the day when panic selling overwhelmed the New York Stock Exchange. The Dow Jones Industrial Average fell 12%, after dropping almost 13% on the preceding Thursday. More than 16 million shares changed hands, setting a trading-volume record that lasted for decades.

Black Tuesday followed a speculative boom in the 1920s, when many investors bought shares with borrowed money. Falling prices then forced leveraged investors to sell, intensifying the decline. The crash did not by itself cause every feature of the Great Depression, but it became its most famous financial symbol.

A common mix-up is Black Thursday, 24 October 1929, the first major panic day. Black Monday is usually associated with the 1987 global crash, not the 1929 collapse.