Steam OS is the primary operating system for the Steam Machine gaming platform by Valve. It is based on the Debian distribution of Linux.

SteamOS is designed primarily for playing video games away from a PC (such as from the couch in one's living room) by providing a console-like experience using generic PC hardware that can connect directly to a television. It can run games natively that have been developed for Linux and purchased from the Steam store. Users are also able to stream games from their Windows, Mac or Linux computers to one running SteamOS, and it incorporates the same family sharing and restrictions as Steam on the desktop. Valve claims that it has "achieved significant performance increases in graphics processing" through SteamOS. The operating system is open source, allowing users to build on or adapt the source code, though the actual Steam client is closed.

Since SteamOS is solely for playing games without use of mouse or keyboard, it does not have many built-in functions beyond web browsing and playing games; for example, there is no file manager or image viewer installed by default. Users can, however, access the GNOME desktop environment and perform tasks like installing other software. Though the OS does not, in its current form, support streaming services, Valve is in talks with streaming companies such as Spotify and Netflix to bring their features to SteamOS. However Steam does have full-length films from indie movie makers available from their store. The OS natively supports Nvidia, Intel, and AMD graphics processors.

Valve stated that it has added support for movies, television, and music functionality to SteamOS, however, the video content is only from Steam's store which has a small number of films, while music playback only supports local music collections. In October 2015, an update allowed Netflix and other DRM protected content to function in the native built-in browser.