A preview of OS X 10.7 Lion was publicly shown at the "Back to the Mac" Apple Special Event on October 20, 2010.

[14] Lion is the first version of macOS that did not support 32-bit processors and is also the final release whose development was overseen by Bertrand Serlet, considered to be the "founding father of Mac OS X".

[15] Although originally paid, Apple later allowed free downloads of the OS, especially for customers of older and no longer officially supported Mac computers, starting on June 30, 2021.

On June 6, 2011, at the Apple Worldwide Developers Conference, it was announced that the official release for Lion would be in July 2011.

[18] Apple did not initially announce any physical media distribution for Lion, such as a set of CD-ROMs or a DVD-ROM as used for past releases.

[2] On August 4, 2011, Apple started to take orders for OS X Lion's USB installation flash drives for $69.99.

[26] Some new features were announced at the "Back to the Mac" keynote in October 2010, and the Apple website was updated in February 2011 with more details.

[74] They noted that it feels like it is the start of a new line of operating systems that will continue to be influenced by Apple's iOS platform.

Ultimately, the magazine considered Lion an operating system worth getting, giving it 4.5 out of 5 stars.

[102] Ted Landau of MacObserver also had serious criticism of Lion, reversing his earlier praise of Autosave and writing, "Auto Save takes irritatingly long when working with large documents.