Which exchange halted trading for four days after the 1987 Black Monday crash?

The Hong Kong Stock Exchange halted trading for four days after the 1987 Black Monday crash.

Hong Kong's market had already fallen sharply before its exchange closed from October 20 through October 23, 1987. The suspension was intended to give brokers and clearing institutions time to manage extreme volatility and unsettled transactions.

When trading resumed on October 26, the Hang Seng Index dropped 33.3% in one session. The Hong Kong decline was among the largest losses in the worldwide crash, which began in the United States on October 19 and rapidly spread across international markets.

The event demonstrated how closely connected global exchanges had become. It also encouraged regulators and exchanges to develop circuit breakers and other procedures intended to slow trading during extraordinary price movements.