Theodore Rshtuni (, also spelled Theodoros Ṛštuni; 590 - 654/655 AD), equated with the patrikios Pasagnathes (Πασαγνάθης) of Theophanes the Confessor, was an Armenian nakharar, famous for resisting the first Arab invasions of Armenia. Rshtuni was appointed as ishkhan and kouropalates of Byzantine Armenia by Emperor Heraclius when the previous ishkan David Saharuni was overthrown by other nakharars.