The software will ship next month and cost $19.99 from the Mac App Store, the company announced at its Worldwide Developers Conference (WWDC).
OS X Mountain Lion will launch with more than 200 different features, including new additions AirPlay Mirroring and PowerNap.
AirPlay Mirroring enables Mac users to screen content onto a television screen via Apple TV, while PowerNap automatically refreshes the data on various devices while a computer is in sleep mode.
"The pace of innovation on the Mac is amazing, OS X Mountain Lion comes just a year after the incredibly successful launch of Lion," said Philip Schiller, Apple's senior vice president of worldwide marketing.
"With iCloud built right in and the new Notification Centre, Messages, Dictation, Facebook integration and more, this is the best OS X yet."
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iOS service iMessage will be coming to Mac computers with the new operating system, and turn-based, head-to-head gaming, and crossplay with iOS devices will be added through GameCentre.
The Mountain Lion upgrade will be free with new laptops.
Picture gallery - Apple's Worldwide Developers Conference announcements:
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