South Korea’s stock market had one of its worst days of the year on Thursday, October 15, 2026. The benchmark KOSPI index fell 454.59 points, or 7.57 percent, to close at 5,554.22. That is its lowest close since April 7 and its seventh losing session in a row, the longest such streak since September 2024. The smaller KOSDAQ index dropped 7.65 percent to 760.82.
The selling was so fierce that trading was paused. At its worst, the KOSPI was down more than 9 percent, which set off a circuit breaker that halted the market for 20 minutes. It was the first time that had happened since late July and the tenth time this year. Local media quickly called it “Black Thursday.”
Two worries hit at once. The first came from the United States, where September consumer prices rose 3.7 percent from a year earlier and producer prices jumped 6.3 percent, well above forecasts. Hotter inflation revived fears that the Federal Reserve could raise interest rates again, which tends to hurt fast-growing technology stocks first.
The second worry was about artificial intelligence itself. Investors are asking whether the enormous amount of money being poured into data centers will ever pay for itself. Rising yields on bonds issued by cloud provider CoreWeave and a slower-than-hoped revenue update from a leading AI developer added to the doubts.
South Korea is especially exposed. Chipmakers Samsung Electronics and SK Hynix, both huge suppliers of memory for AI servers, make up a large share of the index. Samsung fell 9.5 percent and SK Hynix lost 11.1 percent. Neighboring Taiwan, also chip-heavy, fell less than half as much.
On Friday morning the KOSPI bounced back by around 2 to 3 percent, but foreign investors kept selling, and analysts in Seoul warned that a quick V-shaped recovery looks unlikely.
