South Korea’s benchmark stock index, the KOSPI, experienced a dramatic swing on May 15, 2026, briefly surpassing the historic 8,000-point mark before plunging 6.12% to close at 7,493.18. The surge was fueled by momentum from Wall Street and strong performance in AI-related and semiconductor stocks, but the rally quickly reversed as foreign investors cashed in gains. The sell-off, the largest in months, was amplified by renewed geopolitical concerns after U.S. President Donald Trump signaled impatience with Iran following his visit to China, pushing global oil prices higher.

Foreign investors sold 5.6 trillion won in shares, marking their seventh consecutive day of net selling, while institutions offloaded another 1.7 trillion won. Retail investors stepped in, buying 7.2 trillion won, but couldn’t offset the broader downturn. The market’s top performers, including Samsung Electronics and SK hynix, led the decline, dropping 8.61% and 7.66% respectively, amid profit-taking and specific company risks like a looming labor strike at Samsung.

The Korean won weakened to 1,500.8 per U.S. dollar, its lowest in over a month, and bond prices fell as yields rose. While most sectors declined, LG Electronics surged 10.83% on robotics growth expectations, and Doosan Robotics jumped nearly 19%. The event highlights how quickly investor sentiment can shift even after reaching symbolic milestones, especially when global tensions and profit-taking converge.