Debian (/ˈdɛbiən/) is a free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kernel, and is the basis of many other Linux distributions.
As of September 2025, Debian is the second-oldest Linux distribution still in active development; only Slackware is older. The project is coordinated over the Internet by a team of volunteers guided by the Debian Project Leader and three foundation documents: the Debian Social Contract, the Debian Constitution, and the Debian Free Software Guidelines.