The firm's share price has risen by around 5,800% since co-founder and former chief executive Steve Jobs unveiled the first iPhone in 2007.
However, its value slipped a little from that milestone, to end Monday's trading session in New York at $2.99tn.
Apple has been one of the big winners of the pandemic, as coronavirus lockdowns saw spending on gadgets jump.
"Hitting $3 trillion is another historical moment for Apple as the company continues to prove the doubters wrong," Dan Ives, an analyst from Wedbush said.
It took just over 16 months for Apple's stock market valuation to rise from $2tn to $3tn, as the world's biggest technology companies saw demand soar as people became more reliant on smartphones, tablets and laptops during lockdowns.