Mac OS X Panther (version 10.3) was the fourth major release of Apple's macOS operating system, released on October 24, 2003.[1] Some of the key features of Panther included:

- Refined Aqua user interface theme
- Exposé, a feature that allowed users to quickly view all open windows[1]
- Fast user switching, enabling multiple users to be logged in simultaneously[1]
- A new Finder application with a brushed metal interface, live search, and other improvements[1]
- Safari as the default web browser, replacing Internet Explorer[1]
- New applications like Font Book, FileVault, and iChat AV[1]
- Support for the X Window System through an optional install[1]

Panther's system requirements included a PowerPC G3, G4, or G5 processor, at least 128MB of RAM (256MB recommended), and 1.5GB of available hard disk space.[1] It was the first version of macOS to officially support the X Window System for Unix applications.[1] Panther also continued to support the Classic environment for running older Mac OS 9 applications, though with some compatibility issues.