IRIX是由硅谷图形公司（Silicon Graphics Inc.，一般用简称：SGI）以System V与BSD延伸程序为基础所发展成的UNIX操作系统，IRIX可以在SGI公司的RISC型电脑上运行，即是采行32比特、64比特MIPS架构的SGI工作站、服务器。

2006年9月6日，SGI宣布于同年12月起终止MIPS IRIX操作系统产品线。之后SGI电脑的操作系统改为Red Hat Enterprise Linux或SuSE Linux Enterprise Server。IRIX的支持服务持续到2013年12月为止。

IRIX is a discontinued operating system developed by Silicon Graphics (SGI) to run natively on their MIPS workstations and servers. It is based on UNIX System V with BSD extensions. IRIX was the first operating system to include the XFS file system.

The last major version of IRIX was IRIX 6.5 which was released in May 1998. New minor versions of IRIX 6.5 were released every quarter until 2005; since then there have been four further minor releases. Through version 6.5.22, there were two branches of each release: a maintenance release (identified by an m suffix to the version number) that included only fixes to the original IRIX 6.5 code, and a feature release (with an f suffix) that included improvements and enhancements. An overlay upgrade from 6.5.x to the 6.5.22 maintenance release is available as a free download, whereas versions 6.5.23 and higher require an active Silicon Graphics support contract, despite only running on Silicon Graphics hardware.