Key facts
- Seoul stocks closed down 3.26% on Monday, September 14, 2026.
- The KOSPI index fell 225.54 points to 6,684.37.
- Investor sentiment was dampened by Middle East geopolitical uncertainties and concerns over the pace of AI development.
- Brent crude oil hovered above $108 per barrel.
- Samsung Electronics shares fell 4.05%, and SK Hynix shares retreated 6.35%.
- Financial stocks like KB Financial and Shinhan Holdings saw gains.
Seoul stocks tumbled by more than 3 percent on Monday, September 14, 2026, as investors sold off tech-heavyweights amid persisting geopolitical uncertainties and warnings from U.S. tech executives about the rapid pace of artificial intelligence (AI) development. The Korean won also fell against the U.S. dollar.
The benchmark Korea Composite Stock Price Index (KOSPI) closed down 225.54 points, or 3.26 percent, to 6,684.37. Trade volume was light at 274.4 million shares worth 20.19 trillion won (US$14.93 billion), with losers outnumbering winners 561 to 308.
Retail investors were net buyers, snapping up 2.97 trillion won, while institutional and foreign investors offloaded a combined net 4.46 trillion won.
"The main factor that led the sharp decline was the controversy over the pace of AI development," said Lee Kyoung-min, an analyst from Daishin Securities. He added that an anticipated meeting expected to reopen transit in the Hormuz Strait was postponed, which led Brent crude, the international oil benchmark, to hover above US$108 per barrel, further cooling investor sentiment.
Over the weekend, Anthropic's co-founder Dario Amodei issued a proposal to slow down the advancement of AI technology to ensure public safety, a sentiment that was followed by a rare show of unity from other AI executives from the United States.
In Seoul, most market heavyweights ended lower. Top-cap Samsung Electronics shed 4.05 percent to 249,000 won, and rival SK Hynix retreated 6.35 percent to 1,697,000 won. Battery maker LG Energy Solution dipped 2.36 percent to 351,500 won, carmaker Hyundai Motor slid 2.88 percent to 371,500 won.
However, defense giant Hanwha Aerospace jumped 5.18 percent to 1,137,000 won. Financial stocks strengthened on anticipation that the central banks from South Korea and the U.S. will maintain a monetary tightening stance for a longer-than-expected period. KB Financial added 2.08 percent to 181,600 won, and Shinhan Holdings inched up 1.51 percent to 114,600 won.
The Korean won was quoted at 1,347.3 won against the U.S. dollar, down 1.4 won from the close of the previous stock trading session. Bond prices closed lower, with the yield on three-year Treasurys rising 1.1 basis points to 4.025 percent, and the return on the benchmark five-year government bonds adding 1.2 basis points to 4.279 percent.