The 1987 market crash in Hong Kong that helped trigger worldwide panic was called Black Monday.
Hong Kong’s Hang Seng Index fell 11.1% on October 19, 1987, as international selling intensified. Because Hong Kong traded earlier than European and American markets, its collapse became part of the sequence of market falls that moved westward through the global time zones.
The Hong Kong Stock Exchange then closed for four days, reopening on October 26 after the turmoil had spread. When trading resumed, the Hang Seng fell another 33.3%, illustrating how exceptional the episode was.
The name Black Monday is also used for the United States’ October 19 decline, where the Dow lost 22.6%. These were connected events on the same date, but the Hong Kong market had its own scale, trading schedule, and follow-up closure.