Apple is the world's most valuable company, ever.
Overnight, its surging share price propelled the company's value to $US621 billion ($A598 billion), beating the record for market capitalisation set by Microsoft in the heady days of the internet boom.
Apple's stock has hit new highs recently because of optimism around what is believed to be the impending launch of the iPhone 5, and possibly a smaller, cheaper iPad.
Apple has been the world's most valuable company since the end of last year.
It's now worth 53 per cent more than No.2 Exxon Mobil Corp.
The comparison to Microsoft does not take inflation into account.
In inflation-adjusted dollars, the software giant was worth about $US850 billion on December 30, 1999. Microsoft is now worth $US257 billion.