In the Halo universe, an Arbiter is a ceremonial, religious, and political rank bestowed upon Covenant Elites. In the 2004 video game Halo 2, the rank is given to a disgraced commander named Thel 'Vadam as a way to atone for his failures. Although the Arbiter is intended to die serving the Covenant leadership, the High Prophets, he survives his missions and the Prophets' subsequent betrayal of his kind. When he learns that the Prophets' plans would doom all sentient life in the galaxy, the Arbiter allies with the Covenant's enemies (humans) and stops the ringworld Halo from being activated. The Arbiter is a playable character in Halo 2 and its 2007 sequel Halo 3. The character also appears in Halo 5: Guardians and additional expanded universe material. A different Arbiter, Ripa 'Moramee appears in the 2009 real-time strategy game Halo Wars, which takes place 20 years before the events of the main trilogy.

Halo is a military science fiction media franchise, originally developed and created by Bungie and currently managed and developed by 343 Industries, part of Microsoft's Xbox Game Studios. The series launched in 2001 with the first-person shooter video game Halo: Combat Evolved and its tie-in novel, The Fall of Reach. The latest main game, Halo Infinite, was released in late 2021.