freedesktop.org (fd.o) is a project to work on interoperability and shared base technology for free-software desktop environments for the X Window System (X11) and Wayland on Linux and other Unix-like operating systems. It was founded by Havoc Pennington, a GNOME developer working for Red Hat in March 2000. Some of the project's servers are hosted by Portland State University, sponsored by Hewlett-Packard, Intel, and Google.

Widely used open-source X-based desktop projects, such as GNOME, KDE's Plasma Desktop, and Xfce, are collaborating with the freedesktop.org project. In 2006, the project released Portland 1.0 (xdg-utils), a set of common interfaces for desktop environments. However, freedesktop.org is a "collaboration zone" for standards and specifications where users can freely discuss ideas, and not a formal standards organization.

freedesktop.org was formerly known as the X Desktop Group, and the abbreviation "XDG" remains common in their work.

freedesktop.org joined the X.Org Foundation in 2019.

All freedesktop.org projects are covered by Coraline Ada Ehmke's Contributor Covenant code of conduct which aims to ensure a harassment-free and inclusive environment for developers by prohibiting offensive language and behavior.