Symbian is an open source operating system (OS) designed for mobile devices and smartphones, with associated libraries, user interface, frameworks and reference implementations of common tools, originally developed by Symbian Ltd. It was a descendant of Psion's EPOC and runs exclusively on ARM processors, although an unreleased x86 port existed.

In 2008, the former Symbian Software Limited was acquired by Nokia and a new independent non-profit organisation called the Symbian Foundation was established. Symbian OS and its associated user interfaces S60, UIQ and MOAP(S) were contributed by their owners to the foundation with the objective of creating the Symbian platform as a royalty-free, open source software. The platform has been designated as the successor to Symbian OS, following the official launch of the Symbian Foundation in April 2009. Symbian was officially released into Open source world in Feb 2010 .