High Quality Content by WIKIPEDIA articles! OS X Mountain Lion (version 10.8) is the ninth major release of OS X (formerly Mac OS X), Apple Inc.`s desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012. It gains features from iOS, such as Notes and Reminders as applications separate from Mail and Calendar, in addition to those iOS features introduced in Mac OS X Lion. The latest update, rolled out on September 19, 2012, added some extra features such as Facebook integration.