Chrome OS is a Gentoo Linux-based operating system designed by Google. It is derived from the free software Chromium OS and uses the Google Chrome web browser as its principal user interface. Unlike Chromium OS, Chrome OS is proprietary software.

Google announced the project, based on Ubuntu, in July 2009, conceiving it as an operating system in which both applications and user data reside in the cloud: hence Chrome OS primarily runs web applications. Source code and a public demo came that November. The first Chrome OS laptop, known as a Chromebook, arrived in May 2011. Initial Chromebook shipments from Samsung and Acer occurred in July 2011.

Chrome OS has an integrated media player and file manager. It supports Progressive Web Apps and Chrome Apps; these resemble native applications, as well as remote access to the desktop. As more Chrome OS machines have entered the market, the operating system is now seldom evaluated apart from the hardware that runs it.