What was the first day of the 1987 global stock-market crash commonly called?

The first day of the 1987 global stock-market crash is commonly called Black Monday.

Black Monday was October 19, 1987, when stock markets around the world plunged. The Dow Jones Industrial Average lost 22.6%, while other major markets also recorded dramatic falls. The label became especially associated with the U.S. session, but the shock was international and trading hours meant that different markets experienced their major declines on nearby calendar dates.

The crash followed a strong bull market and came amid concerns about valuations, interest rates, currency tensions, and the U.S. trade deficit. Computerized trading strategies, including portfolio insurance, added selling pressure as prices dropped. Researchers generally treat the crash as the result of interacting financial and market-structure factors rather than a single news event.

Black Monday should not be confused with Black Monday in 1929, a separate major selling day during the Wall Street Crash. The 1987 event is distinctive because the one-day percentage loss in the Dow remains unmatched.