South Korea's KOSPI plunges nearly 10% as Samsung and SK Hynix tumble

On 23 June 2026 the South Korean benchmark index KOSPI fell 9.99%, the steepest intraday decline since its inception. The drop was driven by a sharp sell‑off in the two heavyweight semiconductor stocks Samsung Electronics and SK Hynix, each losing about 12 % and accounting for a large share of the index’s market‑cap weighting.

The rapid fall triggered the market’s circuit‑breaker mechanisms, halting trading for 20 minutes after the index slipped more than 8 % and later suspending activity again when the decline continued. Analysts linked the volatility to a broader pattern: the KOSPI has experienced 33 trading halts in the preceding six months, an effect of the concentration of the market in a small number of chaebol groups, whose combined holdings now exceed 60 % of total market value.

South Korean President Lee Jae‑myung has pledged reforms to address the “Korea discount” and the dominance of conglomerates, including new rules on stock‑repurchase and dividend payouts. The crash underscores the systemic risk posed by the over‑reliance on a few large firms and has prompted calls for tighter market‑structure oversight.

The event is expected to weigh on domestic investors and could ripple through regional markets that track Korean semiconductor performance.