Giedi Prime is the name of a fictional planet set in Frank Herbert's Dune universe described in the Dune science fiction novels. It is the home world of the vicious House Harkonnen who are the sworn enemies of House Atreides.
Giedi Prime is a mostly barren planet orbiting a low intensity sun, providing only about a quarter of the luminosity of our sun. The little vegetation the planet provides, comprises mostly low-photosynthetic creeping plants like the inkvine (see Dune_terminology). Rich in mineral resources, the economy of the planet is based on mining, industrial manufacture and refining. Heavy pollution and a destroyed environment lead to a concentration of the planet's population in massive hive-like arcologies. The largest of those is simply called "The Barony" and houses the centre of Harkonnen power. The dismal living conditions on the planet and the low sunlight result in a comparatively sickly and pallid look of the planet's inhabitants.
Due to it's ravaged environment, Giedi Prime has to import almost all of it's requirement of organic products. The Harkonnen have sought to compensate this weakness by military power and conquest. Society on Giedi Prime is martial and darwinistic; gladiatorial games are a common form of entertainment, particularly for nobility, and vocational combat training from an early age is common in all classes of society. Slavery is legal and common, and legal punishment is usually draconian. Such conditions, form the basis for a vast military-industrial complex and an army conditioned by fear which makes House Harkonnen the sole contender for House Atreides - or the throne - in terms of military power.
Giedi Prime wasn`t always the industrial wasteland that is depicted in the original Dune novels and movies. Before the Butlerian Jihad, Giedi Prime was more pleasant in climate and appearance. Due to war and subsequent rule by House Harkonnen, the planet deteriorated to the state it is in during the time of Paul Atreides.
Following the novel God Emperor of Dune, Giedi Prime is renamed Gammu.