The GNOME Structured File Library (GSF) is an I/O abstraction for reading/writing compound files. GSF is released under the GNU Lesser General Public License (GNU LGPL), which allows for flexible licensing of client applications.

GSF was written as part of the Gnumeric project. It started in 2002 as a replacement for libole2 which Gnumeric was using to handle the Microsoft Excel® file format, as libole2's code had become difficult to maintain and was difficult to generalize. GSF was designed to be a more general library for dealing with a number of different types of structured data files and streams.