Arii may refer to:

  • Arii, a Latinized form of Greek Αρειοί ("Ar(e)ioi"), an adherent of the Arian branch of Christianity
  • Arii, the inhabitants of Aria (region), a north eastern Satrapy of the Achaemenid Empire
  • Arii, according to Herodotus the original name of the Medes
  • Ari'i or Ariki, Polynesian nobility
  • Another name for Harii, a Germanic tribe of the 1st century