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.
