Mustafar is a fictional exoplanet in the Star Wars universe. It is depicted in Star Wars Episode III: Revenge of the Sith.

The planet is covered by hundreds of caldera, most of which are in a state of constant eruption. The volcanic activity is caused by gravitational stresses on the planet created by the two gas giants that affect its orbit (similar to Jupiter's Galilean moons). An automated energy and mineral collection facility on the planet is used by the Separatist Council as their last headquarters

Despite its hellish conditions, Mustafar has developed native lifeforms. A sentient race known as Mustafarians developed in the cooler hollows of the planet. They are divided into two subspecies: the tall, thin Northern Mustafarians (led by the enigmatic "Maverick Main") and the shorter, hardier Southern Mustafarians (aka "The Mustafar Rats"). The Techno Union took an interest in the planet and the mineral-rich molten rivers covering its surface, and employed the Mustafarians to mine these minerals. The Mustafarians made use of native "lava fleas," as well as the Techno Union's technology that gave them further protection from the heat. The natives had little interest in outworld politics and were content to work on their homeworld.

As a planet controlled by the Techno Union, Mustafar was a member of the Confederacy of Independent Systems, but remained largely untouched by the Clone Wars. As the war progressed, Count Dooku and the Separatist Council saw fit to build a fortified stronghold on Mustafar to be used in the event that the war against the Galactic Republic did not go well. The Techno Union, the Commerce Guild and the Trade Federation funded the costly fortress, which was designed to be able to withstand any prolonged assault. Mustafar's terrain and environment made it difficult enough to reach the bunker, but it was designed so that even if enemies could negotiate the terrain, they would be unable to take the fortress. Tractor beam and ray shield technology protected it from the lava rivers and its interior chambers were climate-controlled. This bunker was the setting for the duel between Darth Vader and Obi-Wan Kenobi.