Arus is a planet from Voltron: Legendary Defender and the home of the Arusians.
10,000 years ago, King Alfor of Altea sent the Castle of Lions to Arus to keep it hidden from the Galra Empire under Emperor Zarkon. The Arusians, knowing nothing of its origins or nature, came to believe it was the home of a "Lion Goddess" and worshiped her. This would change with the arrival of five humans from Earth, who came aboard the Blue Lion of Voltron after discovering it on their home planet. This set off a chain of events that led to a battle between Voltron and a Galra ship, and later to the Paladins training to form Voltron. Taking the destructive forces unleashed as a sign of divine displeasure, the Arusians sent their warrior Kylzap to find answers, and were thus introduced to the newly formed Defenders of the Universe.
The Paladins would soon befriend the Arusians, and defend them from an attacking Robeast and later when Commander Sendak attacked their village. Allura also gave the King of the Arusians a device he could use to contact the Castle of Lions once it left the planet, making Arus the first planet to join the "Voltron Alliance", a reborn version of King Alfor's ancient coalition. The castle subsequently departed the planet.