The record-breaking session saw chipmaker SK Hynix surge as much as 5.2% to its own all-time high, while Samsung Electronics gained 2.6%. The KOSPI’s advance on April 21 erased all the losses the index had suffered since the Iran war broke out in late February 2026, completing a remarkable V-shaped recovery in less than two months.
SK Hynix Triggers the AI Rally
The primary catalyst for Tuesday’s record-breaking session was news that SK Hynix, South Korea’s second-largest semiconductor company and the world’s largest producer of high-bandwidth memory (HBM) chips, had begun mass production of a key memory module for advanced AI processors made by NVIDIA Corporation. SK Hynix’s HBM3E chips are critical components in NVIDIA’s flagship H100 and H200 AI processors, which are in extraordinary demand from data centers and AI companies worldwide.
The announcement confirmed SK Hynix’s dominance in the HBM segment and validated investor expectations that the AI infrastructure boom would continue to drive exceptional demand for advanced memory chips. The company had already reported strong first-quarter 2026 earnings, with AI chip revenues significantly exceeding analyst estimates.
Samsung Electronics also benefited from the same AI tailwinds, as the company has been racing to close the gap with SK Hynix in the high-margin HBM segment. Strong quarterly trade data from South Korea, released ahead of the market session, showed exports of semiconductor products surging year-on-year, providing additional fundamental support for the rally.
The KOSPI’s Extraordinary Run
The April 21 record is the latest chapter in the KOSPI’s extraordinary multi-year bull run, which has been largely driven by the global artificial intelligence boom. The index has risen approximately 52% in 2026 alone, following a staggering 76% jump in 2025 — the biggest annual gain since 1999. This makes the KOSPI one of the best-performing major stock indices globally over this two-year period.
The index first broke the 5,000 level in early 2026 and then surged through 6,000 and 6,300 in February, before the Iran war-induced selloff temporarily erased those gains. The swift recovery and the new record closing high of 6,388.47 on April 21 demonstrate the underlying strength of investor confidence in South Korean technology stocks.
South Korea’s emergence as a global AI investment destination reflects the country’s remarkable industrial transformation. Samsung Electronics and SK Hynix together control approximately 60-70% of the global DRAM market and dominate the rapidly growing HBM market that is essential for AI computing infrastructure.
Corporate Governance Reforms Boost Investor Confidence
Beyond the AI factor, South Korea’s stock market has also benefited from corporate governance reforms implemented under President Lee Jae Myung, who took office in 2025. The reforms aimed to address the “Korea discount” — the historical tendency for Korean stocks to trade at lower valuations than global peers despite strong fundamentals. Measures including improved shareholder returns, mandatory dividend policies and enhanced transparency have attracted significant foreign institutional investment.
President Lee flagged the concept of a “Korea premium” to replace the long-standing “Korea discount,” and April 21’s record high validates the success of those reform efforts. Foreign investors who had previously avoided Korean equities due to governance concerns have been returning to the market in large numbers throughout 2025 and 2026.
Taiwan Also Gains as Asia AI Trade Accelerates
The AI-driven rally was not confined to South Korea. Taiwan’s TAIEX also gained 1.7% on April 21, as companies in the AI supply chain — including semiconductor foundry TSMC and advanced packaging specialists — attracted strong buying interest. Bloomberg analysis noted that Taiwan is gaining favor over South Korea in some aspects of the Asia AI trade, particularly in advanced chip manufacturing and packaging.
Market Outlook
Analysts tracking the KOSPI remain broadly bullish, citing the structural demand for AI chips as a long-term growth driver that is unlikely to abate even if there are short-term geopolitical disruptions. The continued buildout of AI data centers globally, the proliferation of AI applications across industries, and South Korea’s unique competitive position in memory chip manufacturing all point to sustained investor interest in Korean equities. The April 21 record high is widely seen not as a ceiling but as a milestone on a continuing upward trajectory for one of Asia’s most dynamic and technology-focused stock markets.