OS X 10.7 Lion (Barolo)

Mac OS X Lion (version 10.7)is the eighth major release of Mac OS X (now named macOS), Apple's desktop and server operating system for Macintosh computers.

A preview of Mac OS X 10.7 Lion was publicly shown at the "Back to the Mac" Apple Special Event on October 20, 2010. It brought many developments made in Apple's iOS, such as an easily navigable display of installed applications, to the Mac, and includes support for the Mac App Store, as introduced in Mac OS X Snow Leopard version 10.6.6. On February 24, 2011, the first developer's preview of Lion (11A390) was released to subscribers to the Apple Developer program. Other developer previews were subsequently released, with Lion Preview 4 (11A480b) being released at WWDC 2011.

Lion was released to manufacturing on July 1, 2011, followed by its final release via the Mac App Store on July 20, 2011. Apple reported over one million Lion sales on the first day of its release. As of October 2011, Mac OS X Lion had sold over six million copies worldwide.

Lion is the final release whose development was overseen by Bertrand Serlet, considered the "founding father of Mac OS X".