South Korea's main stock market index, the KOSPI, surged roughly 18% [1] on Friday, July 31, 2026, marking its largest intraday gain on record.
The rally signals a volatile recovery for the Seoul Stock Exchange after a period of extreme instability that wiped hundreds of billions of dollars [4] from market value during a previous three-day sell-off.
The index climbed by more than 1,000 points [2]. This growth was fueled by renewed optimism in artificial-intelligence and semiconductor stocks, which were supported by strong U.S. tech earnings and massive foreign buying [1, 3].
Semiconductor giants Samsung and SK Hynix saw a 28% rise [3]. The surge in these heavyweights contributed significantly to the overall index jump as investors returned to the chip sector following earlier losses [1, 3].
Beyond tech earnings, the market was bolstered by coordinated currency-market intervention between Japan and South Korea [3]. These actions aimed to stabilize the yen and won, creating a more favorable environment for international investors to enter the Korean market [3].
The recovery follows a sharp rout in chip stocks that had previously shaken investor confidence. The scale of Friday's rebound reflects a rapid shift in sentiment toward AI-related assets, which remain the primary engine of the KOSPI's valuation [1, 3].
“The KOSPI index surged by roughly 18% in a single trading day, its largest intraday gain on record.”
The record-breaking surge demonstrates the KOSPI's extreme sensitivity to the global AI trade and U.S. tech performance. While the 1,000-point gain recovers significant lost ground, the volatility—swinging from a multi-billion dollar sell-off to a record rally—highlights the precarious nature of semiconductor-heavy indices in an era of rapid AI speculation and currency instability.
