Apple has just announced that OS X Mountain Lion is the most successful launch of Mac OS X ever, with over three million copies sold in four days.

“Just a year after the incredibly successful introduction of Lion, customers have downloaded Mountain Lion over three million times in just four days, making it our most successful release ever,” said Philip Schiller, Apple’s senior vice president of Worldwide Marketing.

Last year, Apple sold over 1 million copies of OS X Lion in the first day of release. It looks like Apple managed to not just match that rate, but exceed it with Mountain Lion.

Apple’s press release is after the jump. Have you updated to Mountain Lion yet?