US memory chip stocks plunge following South Korean market crash

Shares of SanDisk, Micron Technology, and Western Digital fell sharply on Tuesday, 11%, 10%, and 10% respectively, following a 10% crash in South Korea's Kospi index. The sell-off in US-listed memory giants was triggered by a broader risk-off wave in Asian markets, which saw South Korean peers SK Hynix and Samsung Electronics drop over 12%. Trading in South Korea was briefly suspended for approximately 20 minutes to curb the cascade.

The decline occurred immediately after all three companies closed at record highs on Monday, reversing significant year-to-date gains driven by AI-related demand. SanDisk shares closed at $2,027.50, Micron at $1,085, and Western Digital at $658. The Roundhill Memory ETF (DRAM) also fell 14%, reflecting contagion across the sector despite differing product mixes, such as SanDisk and Western Digital’s focus on NAND and HDD versus pure DRAM exposure.

Despite the sharp price decline, underlying fundamentals remain strong. SanDisk reported a 645% year-on-year surge in datacentre revenue for its third quarter of fiscal 2026, with total revenue of $5.95 billion beating the $4.73 billion consensus. Micron guided for $33.5 billion in third-quarter revenue, following a previous quarter with $23.86 billion in revenue and a 74% gross margin.

Sentiment indicators show a notable cooling among retail investors. Micron’s aggregate sentiment on Reddit slipped from 81 (Very Bullish) to 56 (Neutral), and SanDisk’s slid from 72 (Bullish) to 45 (Neutral). StockTwits sentiment for both Micron and SanDisk turned bearish overnight, consistent with broad de-risking across high-beta AI plays.

The next key market catalyst is Micron's earnings report scheduled for Wednesday, 24 June 2026. Investors are closely watching how the memory complex behaves leading up to the report, which is expected to set the tone for the sector after the recent volatility.