A Guild Navigator (alternately Guildsman or Steersman) is a fictional humanoid in the Dune universe created by Frank Herbert. In this series and its derivative works, starships called heighliners employ a scientific phenomenon known as the Holtzman effect to "fold space" and thereby travel great distances across the universe instantaneously. Humans mutated through the consumption of and exposure to massive amounts of the spice melange, Navigators are able to use a limited form of prescience to safely navigate interstellar space. Control of these Navigators gives the Spacing Guild its monopoly on interstellar travel and banking, making the organization a balance of power against the Padishah Emperor and the assembled noble Houses of the Landsraad.