The 1987 worldwide stock-market crash is known by the nickname Black Monday.
The name most directly refers to October 19, 1987, when the Dow Jones Industrial Average fell 22.6 percent. Markets in other regions also suffered dramatic declines, including Hong Kong, Australia, the United Kingdom, and Canada. Because financial markets operate across time zones, the shock moved around the world over several trading sessions.
The nickname can be confusing because “Black Monday” is also used for other financial and political events. In stock-market history, the unqualified term usually means the 1987 crash. The 1929 collapse has its own labels, including Black Thursday, Black Monday, and Black Tuesday for different trading days.
The 1987 episode encouraged international cooperation among regulators and central banks. It also contributed to the development of circuit breakers and other mechanisms intended to slow disorderly trading. Although the fall was extraordinary, the United States economy did not enter a depression like the one associated with the 1929 crash.