Seoul — August 11, 2026. Published after the market close; prices are official closing values.
The 30-second version
- The KOSPI closed at 6,345.53, up 0.73%, after sliding to the 6,213 area early and touching roughly 6,405 intraday.
- Samsung Electronics did most of the work, jumping 4.13% to 239,500 won.
- The tech-heavy KOSDAQ finished at 857.84, up just 0.39% after being up as much as about 1.8% during the session.
- Foreign and institutional investors were net buyers on the KOSPI; intraday data showed both groups selling the KOSDAQ hard while retail investors bought.
- Oil jumped about 5% in the August 10 session on stalled US-Iran talks over the Strait of Hormuz, and the won weakened to around 1,417 per dollar.
- US CPI and PPI reports due this week are the next big catalysts.
Samsung Electronics did the heavy lifting
Today’s rally was less a broad wave than a single powerful engine. The KOSPI opened weak, sinking to around 6,213 in early trade, before a surge in Samsung Electronics pulled the whole index higher. At its best the benchmark reached roughly 6,405, then gave part of that back to close at 6,345.53, up 0.73%, as reported in the Seoul Shinmun closing wrap.
Samsung Electronics ended up 4.13% at 239,500 won, with its preferred shares gaining 4.77%. Because Samsung carries an outsized weight in the index, a 4% move in that one stock can lift the entire market on its own — think of it as the flagship towing the fleet. The strength spread through related groups: as of early afternoon, electricals and electronics led sectors with a 2.86% gain, followed by pharmaceuticals (+2.41%), insurance (+2.29%), IT services (+1.99%) and manufacturing (+1.96%). Samsung Life rose 3.21% and Samsung Biologics 2.55%.
Breadth was genuinely healthy — 563 KOSPI stocks advanced against 309 decliners, with 38 unchanged — on turnover of 21.59 trillion won, about $15.2 billion at today’s exchange rate. But not everything worked. LG Energy Solution fell 3.54% as batteries stayed weak, KB Financial dropped 2.97% in a bank-sector pullback, and Hyundai Motor lost 1.23%. Early-afternoon sector data showed transport equipment down 2.83%, food and tobacco off 2.59%, and metals down 2.18%.
Two markets, two very different flow stories
On the KOSPI, the professionals showed up. Foreign investors bought a net 44.6 billion won (about $31 million) and domestic institutions added 31.9 billion won (about $23 million), while retail investors sold 72.4 billion won (about $51 million). Program trading — automated basket orders, often tied to index arbitrage — was a net seller of 37.9 billion won. That combined foreign-and-institutional bid is what defended the index’s early dip and powered the rebound.
The KOSDAQ was the mirror image, with an important caveat: confirmed closing flow data was not available at publication, so the figures below are an intraday snapshot as of 1:31 p.m. At that point, foreigners had sold a net 448.8 billion won (about $317 million) and institutions 128.8 billion won (about $91 million), while retail investors bought a net 563.8 billion won (roughly $398 million). The same pattern was visible at 9:31 a.m., suggesting a day-long standoff between individual buyers and professional sellers — one that retail only partly won, given the index’s fade from a 1.8% intraday gain to +0.39%.
Where did that retail money go? Largely into semiconductor equipment and materials suppliers — the small and mid-cap firms that sell tools and components to chipmakers — according to Money Today’s report on the buying spree. Jusung Engineering was up roughly 12-13% intraday, Wonik IPS around 4-6%, and PSK about 1-2.7%. Biotech dragged in the other direction, with Alteogen down 7.33% and ABL Bio down 6.09% at points during the session.
Oil is back in the story — and so is the won
The macro backdrop turned less friendly. In the previous completed session (August 10), WTI crude jumped about 5% to $82.13 a barrel, with Brent up a similar amount, as US-Iran negotiations over reopening the Strait of Hormuz stalled and Iran’s parliament reportedly weighed a bill to block US and Israeli vessels from the strait, per VOA’s report. Korea is heavily dependent on imported crude, so a sustained oil spike feeds directly into domestic inflation pressure.
That risk-off mood showed up in the currency. The won had been strengthening since the dollar peaked around 1,555 won in early July, but today the rate climbed about 0.7% back to around 1,417 — a higher number means a weaker won. The US 10-year Treasury yield rose to 4.703%, and in the prior New York session the Dow slipped 0.11%, the S&P 500 fell 0.06% and the Nasdaq lost 0.32% ahead of this week’s US inflation data.
| Measure | Close | Change |
|---|---|---|
| KOSPI | 6,345.53 | +0.73% |
| KOSDAQ | 857.84 | +0.39% |
| USD/KRW | around 1,417 | up about 0.7% (won weaker) |
| Samsung Electronics | 239,500 won | +4.13% |
| WTI crude | $82.13 (Aug. 10 session) | up about 5% |
| US 10-year Treasury yield | 4.703% | higher |
| KOSPI turnover | 21.59 trillion won (about $15.2 billion) | — |
What to watch next
- US CPI and PPI this week — flagged as the key variable for the market’s next directional move.
- The Strait of Hormuz talks — any progress or escalation will drive oil, and with it Korean inflation expectations and the won.
- Confirmed KOSDAQ closing flows — today’s figures were intraday snapshots; the final numbers will show whether foreign selling persisted into the close.
- Follow-through on the KOSPI — whether foreign and institutional buying continues, and whether Samsung’s move extends beyond a single session.
FAQ
Why did the KOSPI rise on August 11, 2026?
Mainly Samsung Electronics, which jumped 4.13% to 239,500 won and, given its heavy index weight, pulled the KOSPI from an early low near 6,213 to a close of 6,345.53. Net buying by foreign investors (44.6 billion won) and institutions (31.9 billion won) supported the rebound.
Why is the Korean won weakening again?
Oil prices jumped about 5% in the August 10 session after US-Iran talks over the Strait of Hormuz stalled, reviving risk aversion toward Korea, a major crude importer. The dollar rose about 0.7% to around 1,417 won, reversing part of the won’s strengthening trend since the rate peaked around 1,555 in early July.
Why did the KOSDAQ underperform the KOSPI today?
Intraday data (as of 1:31 p.m.; closing figures unconfirmed) showed foreigners and institutions selling a combined 577.6 billion won of KOSDAQ shares, with retail buying of about 563.8 billion won only partly offsetting it. Biotech weakness — Alteogen and ABL Bio fell sharply intraday — also weighed, leaving the index up just 0.39% after a 1.8% intraday gain.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.