Hong Kong’s stock exchange crashed on October 19, 1987, beginning the worldwide Black Monday panic.
The Hang Seng Index fell 11.1% on October 19. Selling then spread westward through international markets, reaching Europe and the United States. The Dow Jones Industrial Average lost 22.6% on October 19, the largest one-day percentage decline in its history.
Several factors contributed, including highly valued shares, rising interest rates, currency concerns, program trading, and market structures that amplified selling. No single cause fully explains the global event, and investigations emphasized the interaction of financial and technical pressures.
After the crash, regulators introduced or strengthened safeguards such as trading halts and circuit breakers. A common misunderstanding is that U.S. markets started the episode because the American decline became its best-known image. In chronological terms, Hong Kong experienced the first major collapse of the day, before the panic moved through other time zones.