- SK Hynix surged 29.95% to hit its daily price limit for the first time, while Samsung Electronics jumped 26.81% — both recording their largest single-day gains on record [1] - The KOSPI gained 1,001.89 points to close at 6,595.45, a 17.91% surge that eclipsed the previous record of 11.95% set during the 2008 financial crisis [2] - Microsoft and Amazon earnings overnight eased fears about AI infrastructure spending, triggering an 8% rally in the Philadelphia Semiconductor Index [3] - SK Hynix reported record Q2 operating profit of 60.5 trillion won on a 76% margin, while Samsung's chip profit surged 250-fold year-over-year [4][5] - Foreign investors purchased a net 7.18 trillion won in Korean equities on the session, while retail investors sold 8.25 trillion won
[2] South Korea's stock market posted the largest single-day gain in its history on Friday, as SK Hynix and Samsung Electronics — the world's two largest memory chipmakers — surged nearly 30% on renewed confidence in artificial intelligence infrastructure spending. The KOSPI index jumped 1,001.89 points, or 17.91%, to close at 6,595.45, smashing the previous record of 11.95% set on October 30, 2008 [1] [2].
SK Hynix rose 29.95% to 1.72 million won, hitting its daily upper price limit for the first time in the stock's history. Samsung Electronics climbed 26.81% to 262,500 won. Together, the two companies account for roughly 80% of the global memory chip market by revenue [1] [3].
The rally was triggered by strong overnight earnings from Microsoft and Amazon, which beat forecasts on cloud-computing revenue and reaffirmed heavy AI capital expenditure plans. The Philadelphia Semiconductor Index surged 8.19%, with Micron Technology gaining 18.4% and SanDisk jumping 26% in U.S. trading [3].
The historic rebound followed three consecutive sessions of steep declines in which the KOSPI had shed over 17%, driven by concerns over lofty AI valuations and intensifying competition from Chinese memory chipmakers. Despite Friday's record rally, the index still recorded its worst monthly performance since the 1997 Asian financial crisis, falling 22.19% in July [2].
What Triggered the Rally #
Microsoft's fiscal fourth-quarter earnings, reported after the U.S. close on Wednesday, proved pivotal. The company beat revenue expectations and reported faster-than-anticipated Azure cloud growth, easing investor anxiety that Big Tech's hundreds of billions in AI infrastructure spending would fail to generate returns [3].
Amazon followed with its own earnings beat, sending its shares up roughly 9% in after-hours trading. The back-to-back results from two of the largest buyers of AI accelerators and high-bandwidth memory gave investors the clearest signal yet that demand for the chips SK Hynix and Samsung produce remains robust [3].
The overnight rally in U.S. semiconductor stocks was broad-based. Beyond Micron's 18.4% gain, AMD rose 13%, Intel climbed 11.3%, and the iShares Semiconductor ETF (SOXX) gained 8%. Japanese chipmakers followed suit in Asian trading, with Advantest surging 18%, Disco up 13%, and Tokyo Electron rising 9% [3].
Record Earnings Underpin the Rebound #
The session's extraordinary gains came just days after both SK Hynix and Samsung reported record quarterly earnings, underscoring the fundamental demand backdrop for the rally.
SK Hynix posted Q2 operating profit of 60.5 trillion won on revenue of 79.3 trillion won, delivering a 76% operating margin. Revenue surged 257% year-over-year while operating profit jumped 557%. The company's cumulative first-half revenue exceeded 100 trillion won for the first time in its history [4].
SK Hynix began mass shipments of its HBM4 memory chip during the quarter and finalized multi-year supply agreements with approximately 10 major customers. Cash reserves climbed to 88 trillion won, while total debt declined to 18.6 trillion won [4].
Samsung's semiconductor division reported a profit surge of more than 250-fold year-over-year, with total company revenue hitting 171.5 trillion won — an all-time quarterly record. Samsung scaled HBM4 sales during the quarter and shipped what it described as 'industry-first' HBM4E samples to major customers [5].
Together, the two companies generated approximately 150 trillion won ($104 billion) in combined operating profit in a single quarter [5].
Market Mechanics and Foreign Flows #
Trading volume on the Korea Exchange reached 430.2 million shares worth approximately $34.2 billion. The session was volatile enough to trigger the exchange's 'Sidecar' mechanism at around 9:06 a.m. local time, suspending program trading for five minutes after sharp moves in KOSPI 200 futures [2].
Foreign investors were the dominant force behind the rebound, purchasing a net 7.18 trillion won ($5 billion) in Korean equities. Domestic institutions added 1.18 trillion won. Retail investors, by contrast, sold a net 8.25 trillion won — an unusually large divergence that suggests institutional and foreign money drove the recovery while individuals took profits [2].
The rally extended beyond semiconductors. Automakers and shipbuilders gained 7-10%, defense stocks rose 6-9%, and the secondary KOSDAQ index surged 11.63% to 719.76 [1] [2].
Context: A Brutal July #
The historic single-day rally must be read against an equally historic rout. The KOSPI fell 22.19% during July — its worst monthly performance since the 1997 Asian financial crisis — as investors retreated from AI-linked equities on valuation concerns and fears of Chinese competition in advanced memory [2].
The prior three sessions alone had erased more than 17% of the index's value. Both SK Hynix and Samsung had fallen sharply from mid-July peaks, making Friday's rally in part a mechanical snapback from oversold conditions rather than an all-clear signal [2].
The divergence between devastating monthly losses and a record daily gain echoes October 2008, when the previous single-day record was set amid extreme volatility during the global financial crisis. Whether the KOSPI's rebound holds will depend on sustained earnings delivery from memory chipmakers and continued capital expenditure commitments from hyperscale cloud operators [1] [2].
What's Next #
Both SK Hynix and Samsung are ramping HBM4 production in the second half of 2026, with HBM4E — the next-generation variant offering higher capacity — expected to enter volume production in early 2027. SK Hynix's finalization of long-term supply agreements with roughly 10 major customers provides visibility into demand through at least 2028 [4].
The immediate test for the rally's durability will be whether additional hyperscaler earnings — including from Alphabet and Meta, which report in coming weeks — confirm the AI spending trajectory that Microsoft and Amazon established this week [3].
Companies mentioned #
Further sources #
[[1] Korea Herald — Seoul shares surge record 18% to reclaim 6,500-point level on ch… ↗](https://www.koreaherald.com/article/10827325)
[[2] Asia Business Daily — KOSPI Posts Record Single-Day Gain, Surges Over 1,000 Poi… ↗](https://www.asiae.co.kr/en/article/2026073115513003224)
[[3] Seoul Economic Daily — Breaking News: Samsung Electronics, SK hynix Soar Around… ↗](https://en.sedaily.com/finance/2026/07/31/breaking-news-samsung-electronics-sk-hynix-soar-around-20)
[[4] SK hynix Newsroom — Q2 2026 Business Results ↗](https://news.skhynix.com/en/q2-2026-business-results/)
[[5] Eastern Herald — Samsung Chip Profit Surges 250-Fold on AI Memory Demand ↗](https://easternherald.com/2026/07/30/samsung-chip-profit-ai-memory-demand-q2-2026/)
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