Korea Market Brief — KOSPI's record 17.9% rebound as chip giants roar back (July 31)

Seoul just delivered the single most violent week in the modern history of its stock market — and it ended with the biggest one-day gain the KOSPI has ever recorded. On Friday, July 31, the benchmark rocketed 17.91% to close at 6,595.45, adding 1,001.89 points in a single session and vaulting back above the 6,500 line it had lost only days earlier. This came after a three-day rout that had erased roughly 17% and tripped market-wide circuit breakers on back-to-back days for the first time ever. If you looked away for a week and glanced back, the index is close to where it started — but the round trip in between was extraordinary.

The short version: The KOSPI staged a record 17.91% rebound to 6,595 as Samsung Electronics jumped about 28% and SK Hynix soared roughly 30%, with foreigners pouring in more than 7 trillion won. Microsoft's strong AI cloud results overnight calmed "AI bubble" fears that had crushed Seoul's chip names all week.

What moved the market

One overseas earnings report did most of the heavy lifting. Microsoft reported that its Azure cloud business grew about 43% and crossed $100 billion in annualized revenue while spending on AI infrastructure came in leaner than feared. For a market that had spent the previous three sessions dumping chip stocks on exactly the opposite worry — that hyperscalers were pouring money into AI without the revenue to justify it — that was the antidote. US AI and semiconductor peers rallied overnight, and Seoul, whose index is dominated by memory-chip makers, opened sharply higher and never looked back.

The flows tell the story. Foreign investors bought a net 7.18 trillion won of KOSPI stocks on the day, and institutions added roughly 1.18 trillion won — a stampede back into the names they had been fleeing. That is the mirror image of the prior week, when foreign selling of Korean equities had piled up to near-record levels and helped drive the index down more than 10% in a single day (July 28) alone.

The rebound was concentrated at the very top of the index. SK Hynix climbed close to its 30% daily price limit, aided not only by the US chip bounce but by a rare, direct purchase of shares by SK Group Chairman Chey Tae-won — the kind of insider signal traders latch onto after a brutal selloff. Samsung Electronics rose about 28%. Because those two stocks carry enormous weight in the KOSPI, their move alone was enough to produce a headline number that would be almost unthinkable in a broader, more balanced index.

Sector by sector

This was a chip rally first and everything-else second. Semiconductors and AI hardware led by a wide margin, and the read-through lifted the broader technology and equipment complex — chip toolmakers, materials suppliers, and anything tied to the memory cycle. The KOSDAQ, home to smaller tech and biotech names, jumped 11.63% to 719.76, a strong move but a notably smaller one than the large-cap KOSPI, underlining how top-heavy the day was.

Outside tech, the gains were real but more ordinary. Financials, autos, shipbuilding, batteries and defense participated in the risk-on tone, but none of them defined the session. The simplest way to read Friday is this: the same memory-chip stocks that dragged the index into two straight circuit breakers were the ones that yanked it back out.

The won and the macro picture

Currency moves were muted next to the equity fireworks. The won traded in the 1,430s per dollar, roughly where it had been, after strengthening earlier in the week to around a five-month high. A firmer won and returning foreign inflows tend to reinforce each other, and the calmer tone on Friday kept the currency stable even as stocks went vertical.

The macro backdrop remains the real reason Korea is a global story right now: exports are booming on AI demand. In the first 20 days of July, exports rose 52.3% year on year to $54.9 billion, with semiconductor shipments up around 180% to $22.1 billion. That export strength is also why the Bank of Korea ended a long rate freeze in July and began a tightening cycle — an unusual stance among major central banks — with policymakers arguing the chip-driven boom is stoking growth and inflation rather than fading. The BOK has left the door open to another hike at its next meeting.

The tension in all of this is what whipsawed the market this week. The bull case (surging AI exports, a supply-constrained memory cycle the BOK itself says is "far from over") and the bear case (an AI-spending bubble, rising Chinese chip competition, valuations that had run hard) are both live — and both were on full display within the same five trading days.

What to watch next

• Full July export data, due at the start of August, will show whether the AI-led shipment surge held through month-end. Semiconductors are the number that moves the tape.
• The Bank of Korea's August 27 meeting. With the BOK now in tightening mode and citing the chip boom, markets will parse every signal on whether another 25-basis-point hike is coming.
• Whether the chip rebound sticks. A record one-day gain after a record crash is a sign of how jumpy positioning has become, not proof the selloff is over. Watch foreign flows and the US mega-cap AI names for the next cue.
• Volatility itself. With eight circuit breakers already triggered in 2026 and the first-ever back-to-back halts fresh in memory, wide daily swings are the base case, not the exception.

Friday closed the book on a month that saw Seoul both crash and rebound at record speed. The chip story that powered Korea's rally all year is intact in the export data — but this week was a reminder of how violently sentiment around that same story can turn.

This is market information, not investment advice.