KOSPI Surges 4.89% to 8,885 on Micron Beat, Retail Accounts Hit 108M

A single after-hours earnings report from Idaho-based Micron Technology sent shockwaves across global markets, with Seoul’s KOSPI index recording its largest single-day surge in months. For South Korean retail investors—who now hold a record 108.7 million trading accounts—the 4.89% jump to 8,885.57 wasn’t just a number: it was validation of their heavy bets on local chip champions. As Samsung Electronics gained 4.77% and SK hynix soared 9.61%, the rally demonstrated both the resilience of AI chip demand and the deep integration of Korea’s equity market with global tech sentiment.

The Seoul stock market staged a powerful rally on June 25, 2026, with the benchmark KOSPI index surging 4.89% to 8,885.57, its strongest single-day performance in recent memory. The catalyst was an after-hours earnings report from Micron Technology, the world’s third-largest memory chipmaker, which sharply beat market expectations and wiped away mounting anxiety about overvaluation in artificial intelligence (AI)-related stocks. Just the previous evening, Wall Street had closed mixed amid fears that AI shares were due for a correction, but Micron’s blowout numbers demonstrated that demand for memory chips—the backbone of AI training and inference—remains exceptionally robust. The earnings report, released after the US market close on June 24, immediately reverberated across Asian markets, with Seoul, as the global epicenter of memory production, feeling the most dramatic impact.

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As Samsung Electronics gained 4.77% and SK hynix soared 9.61%, the rally demonstrated both the resilience of AI chip demand and the deep integration of Korea’s equity market with global tech sentiment.

The rally was led by the semiconductor sector. Samsung Electronics, the market bellwether, jumped 4.77%, adding nearly $20 billion to its market capitalization in a matter of hours. Even more explosive was the performance of SK hynix, the leading supplier of high-bandwidth memory (HBM) used in AI accelerators, which soared 9.61%. This jump reflects the direct link between Micron’s earnings beat and the AI memory demand curve. SK hynix commands a dominant share of the HBM market, and investors interpreted Micron’s strong results as confirmation that orders from AI chip designers like NVIDIA remain on a steep upward trajectory. Hanmi Semiconductor, a key equipment maker, rose 2.22%, while LG Electronics added a modest 0.24%, showing that the rally was concentrated in the chip value chain.

The rally also spilled over into financial stocks, as broader market optimism lifted sectors beyond technology. KB Financial Group gained 1.91%, and Samsung Life Insurance climbed an impressive 6.47%. These gains highlight how a tech-led rally can boost investor confidence across the board, particularly among retail investors who have been flooding into the market. Data released the same day by the Korea Financial Investment Association showed that the number of stock trading accounts in South Korea reached a record 108.7 million as of June 24, up from 98.28 million at the end of 2025. This increase of over 10.4 million accounts in just six months underscores a retail investor frenzy that has been concentrated on heavyweight chip stocks. Notably, the KOSPI has surged past the 9,000-point mark earlier this month, reflecting sustained bullish sentiment despite periodic gyrations.