Version 10.5 of the Mac OS X operating system, which runs on PowerPC and Intel-based Macs. Released in October 2007, Leopard includes many enhancements and new features, including Time Machine, an automated backup utility; Spaces, a way to organize applications in separate "virtual" desktops; and Spotlight, a search capability across the network. Boot Camp, which allows users to install Windows on Intel-based Macs, is included rather than being an option.

Numerous enhancements were made to the basic OS X architecture, and several security enhancements were added. For example, Leopard supports code signing, which verifies that executable applications are not tampered with. Address space randomization places code randomly in memory rather than in predetermined locations that hackers are expecting. See Mac OS X and Boot Camp.