KOSPI plunges after tech selloff and U.S. rate worries

South Korea's benchmark KOSPI plunged on June 8, 2026, amid a technology-led selloff and rising concerns about U.S. interest rates. Reporting by UPI states the index lost 676.18 points, or 8.29 percent, to close at 7,484.41, after briefly falling as low as 7,442.73. Reuters reports the drop marked the index's biggest daily decline since March 4 and that the KOSPI is roughly 15% below its June 2 peak of 8,801.49. The secondary KOSDAQ fell more than 9% to 911.39, according to UPI.

UPI reports heavy turnover, with 448.3 million shares traded worth 47.8 trillion won (about US$31.2 billion) and losers outnumbering winners 873 to 42. UPI further reports foreigners and institutions sold about 355.5 billion won and 1.6 trillion won, respectively, while retail investors bought about 1.76 trillion won. Reuters and UPI report the Korea Exchange (KRX) activated circuit breakers shortly after the open and implemented sell-side sidecars for both KOSPI and KOSDAQ during the session.

Reuters reports Samsung Electronics fell 10.2% and SK Hynix dropped 7.7%. UPI documents heavy losses among major U.S. chip stocks as well, citing Nvidia down 6.2%, Broadcom down 7.92%, and Micron down 13.25%. Reuters includes a quote from Nvidia CEO Jensen Huang that SK Hynix remained its "biggest partner" while announcing deals during his South Korea trip.

Reuters and Yahoo report the won reversed from a 17-year low after authorities convened emergency meetings and signaled intervention. Reuters reports the currency traded around 1,533.7 won per dollar after slipping to about 1,615.0 on Friday. Reuters quotes market participants saying authorities were likely to sell dollars to cap won weakness; UPI reports officials engaged in verbal intervention.

The session combined two high-impact drivers for markets that have been concentrated in a few mega-cap chip names: stronger-than-expected U.S. payrolls data, which Reuters and Yahoo link to renewed Fed-hike expectations, and rapid profit-taking in AI-exposed semiconductor stocks after an extended rally. Companies and indexes with outsized weightings in semiconductor firms are, in similar past episodes, especially sensitive to macro data surprises and risk-off flows.

Reporting places the selloff in the broader pattern of 2026 market dynamics where AI-related earnings and hardware demand have heavily influenced equity performance. Observers quoted by Reuters and UPI note that Samsung and SK Hynix accounted for a large share of the KOSPI's year-to-date gains, amplifying index moves when their shares reprice. For practitioners, concentrated sector exposure combined with macro tightening scenarios increases short-term liquidity and execution risk for large orders in local markets.

Market participants will watch incoming U.S. macro data and Fed commentary for signals on policy trajectory, and monitor official FX statements and intervention activity for volatility in the won. Observers will also track quarterly guidance and earnings commentary from major semiconductor suppliers for signs of durable demand versus cyclical shifts. Finally, circuit-breaker and sidecar activations may be an operational constraint for trading strategies that assume continuous market access.