The stock ended trading at $142.19, its lowest price level since July 2017. The plunge makes for Apple's worst day of trading since January 2013, and it extends a painful year-end trend for Apple into 2019.
The stock, which once traded above $230 per share, shed 30 percent in the fourth quarter of 2018.
Thursday's losses push Apple's market valuation below $700 billion and behind the market cap of Alphabet to become the fourth most valuable publicly traded U.S. company — down from the top spot just two months ago. The company has lost $450 billion in market value since its peak of about $1.1 trillion last year.
Apple cited longer upgrade cycles and headwinds in China as causing lower-than-expected iPhone sales. Apple now expects revenue for its fiscal first quarter to be as much as $9 billion lower than previous projections.
It's the admission shareholders had been waiting for, after months of reported supply-chain cuts and a major shake-up to the company's sales reporting structure. Apple said in November it would stop reporting individual unit sales and revenue figures for its main product lines.
As of Thursday's close, Apple has lost 17 percent in the last 12 months, and almost 40 percent since 52-week highs.