SK Hynix suffered its steepest single-session decline in history on Monday, with Korea-listed shares plunging 15.4% to close at 1,845,000 won — a near one-month low — just one trading day after the company completed a landmark $26.5 billion American Depositary Receipt offering in New York that had been celebrated as the largest-ever US listing by a foreign company. The reversal wiped hundreds of billions of dollars in market capitalization off South Korea's most valuable company in a matter of hours.
The sell-off spread rapidly across the Korean market. Samsung Electronics fell 10.7% to 254,500 won as investors fled the semiconductor sector in force, and the benchmark KOSPI index plummeted 8.95% to close at 6,806.93, triggering a 20-minute market-wide circuit breaker — the seventh such halt of 2026, and among the most severe since the pandemic era. The Korea Exchange also activated its 35th sell-side program trading curb of the year, underscoring the degree of automated selling pressure that accumulated during the afternoon session.
Analysts identified a triple catalyst for the rout. First, traders engaged in a classic switch trade, selling Korea-listed shares to fund purchases of the newly listed and more liquid US ADRs trading under the ticker SKHY, which introduced mechanical downward pressure on the Seoul market. Second, Korea Investment & Securities issued a profit forecast showing SK Hynix's second-quarter operating profit at approximately 60.4 trillion won, roughly 8% below the market consensus of 65 trillion won, even though that figure still represents a 556% year-over-year surge. The firm noted that because SK Hynix derives a higher proportion of revenue from High Bandwidth Memory than peers, and HBM contracts typically use longer-term pricing agreements with less flexibility, its average selling price increases have lagged the spot market average. Third, renewed US-Iran airstrikes over the weekend triggered a broad risk-off move across Asian markets, with geopolitical uncertainty amplifying an already fragile technical setup after SK Hynix's stock had already fallen roughly 37% from its June 22 peak before Monday's open.
UBS analyst Charles Lee noted that SK Hynix's 50-day moving average had again failed to hold as support, with the stock breaking below the key 1,845,000 won level that had provided a floor earlier in July. Separately, UBS analyst Justinus Steinhorst observed continued weakness in a basket of AI-linked winners, describing the price action as resembling a short-term peak-narrative unwind rather than a fundamental deterioration in the AI supply chain.
The Bank of Korea attempted to stabilize sentiment by releasing a report reiterating that the global semiconductor market remains in a state of undersupply and that the AI-driven semiconductor super-cycle has not yet peaked. Retail investors responded by buying the dip, with local individual buyers reportedly taking in more than $730 million in Samsung shares alone during the session, while foreign and institutional investors were net sellers of a combined $693 million in Samsung.
In US premarket trading, SK Hynix's ADRs dropped approximately 9% to $153.50. Micron Technology, the primary US-listed memory proxy, was also lower in premarket trading, and the VanEck Semiconductor ETF faced broad sympathy selling across the semiconductor supply chain. The Nikkei 225 in Japan fell 1.92%, and Kioxia, the Japanese memory chipmaker, slumped nearly 13%, reflecting how completely the sell-off engulfed the broader Asian memory ecosystem. Despite Monday's sharp correction, the KOSPI remains the world's best-performing major stock index year-to-date in 2026, still up approximately 63% for the year.