GIO (Gnome Input/Output) is a library, designed to present programmers with a modern and usable interface to a virtual file system. It allows applications to access local and remote files with a single consistent API, which was designed "to overcome the shortcomings of GnomeVFS" and be "so good that developers prefer it over raw POSIX calls."

GIO serves as low-level system library for the GNOME Shell/GNOME/GTK software stack and is being developed by The GNOME Project. It is maintained as a separate library, libgio-2.0, but it is bundled with GLib. GIO is free and open-source software released under the GNU Lesser General Public License.

Beyond these, GIO provides facilities for file monitoring, asynchronous I/O and filename completion. In addition to the interfaces, GIO provides implementations for the local case. Implementations for various network file systems are provided by the GVfs package as loadable modules.