South Korea's Stock Market Posts Record 15% Single-Day Gain

South Korea's main stock index, the Kospi, jumped roughly 15% on July 31, 2026 — its biggest one-day rise ever — after US markets rebounded July 30. A recovery in artificial intelligence stocks pushed Samsung and SK Hynix each up over 20%. The rally follows a steep July sell-off that wiped $2 trillion from the index since June's record high.