GIMP /ɡɪmp/ (GNU Image Manipulation Program) is a raster graphics editor used for image retouching and editing, free-form drawing, resizing, cropping, photo-montages, converting between different image formats, and more specialized tasks.

GIMP is released under LGPLv3 and GPLv3+ licenses and is available for Linux, OS X, and Windows.

GIMP was originally released as the General Image Manipulation Program, by creators Spencer Kimball and Peter Mattis. Development of GIMP began in 1995 as a semester-long project at the University of California, Berkeley; the first public release of GIMP (0.54) was made in January 1996. When Richard Stallman visited UC Berkeley the following year, Kimball and Mattis asked him if they could change General to GNU (the name of the operating system created by Stallman). With Stallman's approval, the definition of the acronym GIMP was changed to mean the GNU Image Manipulation Program, which also reflects its existence under the GNU Project. GIMP is developed by a self-organized group of volunteers under the banner of the GNOME Project.

The number of computer architectures and operating systems supported has expanded significantly since its first release. The first release supported UNIX systems such as Linux, SGI IRIX and HP-UX. Since the initial release, GIMP has been ported to many operating systems, including Microsoft Windows and OS X; the original port to the Windows 32-bit platform was started by Finnish programmer Tor Lillqvist (tml) in 1997 and was supported in the GIMP 1.1 release.

GIMP saw formation of a community and rapid adoption following the first release. The community that formed began developing tutorials, artwork and shared better work-flows and techniques.

A new GUI tool kit called GTK+ (GIMP tool kit) was developed to facilitate the development of GIMP. GTK+ replaced its predecessor GTK (no plus symbol) after being redesigned using object-oriented programming techniques. The development of GTK+ has been attributed to Peter Mattis becoming disenchanted with the Motif toolkit GIMP originally used; Motif was used up until GIMP 0.60.