GrapheneOS is a privacy and security focused mobile OS with Android app compatibility developed as a non-profit open source project. It's focused on the research and development of privacy and security technology including substantial improvements to sandboxing, exploit mitigations and the permission model. It was founded in 2014 and was formerly known as CopperheadOS.

GrapheneOS improves the privacy and security of the OS from the bottom up. It deploys technologies to mitigate whole classes of vulnerabilities and make exploiting the most common sources of vulnerabilities substantially more difficult. It improves the security of both the OS and the apps running on it. The app sandbox and other security boundaries are fortified. GrapheneOS tries to avoid impacting the user experience with the privacy and security features. Ideally, the features can be designed so that they're always enabled with no impact on the user experience and no additional complexity like configuration options. It's not always feasible, and GrapheneOS does add various toggles for features like the Network permission, Sensors permission, restrictions when the device is locked (USB peripherals, camera, quick tiles), etc. along with more complex user-facing privacy and security features with their own UX.