Mac OS X 10.0 (codenamed Cheetah) is the first release of OS X, an operating system made by Apple Inc. It was released on June 22, 2001 for US$129. It is the successor to the Mac OS X Public Beta and the predecessor to Mac OS X 10.1 "Puma".


Mac OS X 10.0 introduced the Aqua user interface, an email application, an address book, a desktop and web search engine, and a basic word processor. It is built on Darwin, a Unix-like operating system. Support for PDFs, OpenGL, AppleScript, the Carbon and Cocoa APIs, and preemptive multitasking was added as well.