South Korea’s Kospi index experienced a sharp retreat on Tuesday, tumbling nearly 10% and recording its largest single-day decline since early March. The downturn followed robust selling of major semiconductor stocks by foreign investors, coming on the heels of regulatory warnings about mounting risks from leveraged investment vehicles and heightened volatility within the sector.
By the close, the index had fallen 910.71 points, or 9.99%, to 8,203.84. The selloff was exacerbated by steep losses in Samsung Electronics and SK Hynix, both of which lost in excess of 12%, erasing billions in capitalization and prompting an automatic 20-minute market-wide trading suspension in the afternoon session.
Regulatory signals played a central role in Tuesday’s rout. Financial authorities recently voiced unease over the pace at which leveraged products tied to semiconductor shares had been approved, with such funds only entering the market a month ago. Officials have warned that the popularity of leverage among retail participants poses additional risk as margin debt, or borrowing to buy stocks, climbed to record highs in June.
News that South Korea would not be upgraded to MSCI’s developed markets index during the forthcoming review further undercut confidence, reducing the likelihood of additional foreign capital inflows that investors had anticipated. This, coupled with the abrupt reversal of the Kospi’s powerful rally—one of the most robust advances globally in 2026—prompted profit-taking as market sentiment turned more cautious.
Meanwhile, the influence of heavyweights Samsung Electronics and SK Hynix on the index has intensified, with both companies now accounting for more than half of the Kospi’s total market value. The previous session saw the benchmark surge past the 9,100 mark for the first time, but the swift change in direction highlighted concerns over valuation stretch.
SK Hynix came under distinct pressure after reports emerged that the company might reduce its output of high-bandwidth memory to favor DRAM, potentially altering its competitive dynamics within the semiconductor space. This follows SK Hynix surpassing Samsung Electronics in market capitalization earlier this week.
Hyundai Motor also contributed to Tuesday’s declines, with shares dropping by over 10%. Nonetheless, semiconductor stocks continue to be the focal point of South Korea’s market story, with the industry remaining a key driver of overall performance.
