For the planet see: Arcturus (planet)
Arcturus was the Arcturan delegate to Peladon when it applied for membership in the Galactic Federation. He aided Hepesh in attempting to prevent Peladon from joining, secretly planning for his world to exploit the planet's mineral wealth afterwards. He attempted to kill the Third Doctor, but was killed by Ssorg. (DW: The Curse of Peladon)