South Korea’s KOSPI Plunges as Samsung, AI Chip Stocks Trigger Market Sell-Off

South Korea’s benchmark KOSPI index tumbled as much as 8% on Tuesday, prompting the Korea Exchange to activate a market-wide sell-side circuit breaker as investors rushed to sell major technology stocks despite Samsung Electronics posting record quarterly earnings.

The sharp decline reflected growing concerns that the artificial intelligence-driven rally in semiconductor stocks had become overextended, leading investors to lock in profits after months of strong gains. The Korea Exchange temporarily halted program trading through a sell-side sidecar mechanism to help stabilize the market following the steep drop.

The KOSPI was last down 5.8% at 7,587.55 during morning trading, with heavyweight chipmakers leading the losses.

Samsung Electronics shares fell as much as 10% to 286,000 won even after the company projected a record second-quarter operating profit of 89.4 trillion won ($58.4 billion). The result marked a 19-fold increase from the same period a year earlier and exceeded analyst expectations, driven by robust demand for high-bandwidth memory chips used in artificial intelligence servers and improved chip pricing.

Despite the strong earnings, investors chose to take profits, signaling broader concerns that soaring valuations across the AI semiconductor sector may have outpaced fundamentals. The stock had rallied significantly in recent months alongside other AI-related companies.

SK Hynix, another major AI memory chip producer, also suffered heavy losses as selling pressure spread across South Korea’s technology sector.

The decline extended beyond individual chipmakers, dragging the broader KOSPI lower and erasing a significant portion of the market’s recent gains. Investors are increasingly questioning whether the rapid expansion of AI-related spending and semiconductor demand can continue at a pace sufficient to justify elevated stock valuations.

Tuesday’s market reaction highlights growing caution among investors as they reassess risks in the AI supply chain, even as semiconductor companies continue to report strong earnings fueled by artificial intelligence demand.