Theodore Rshtuni (590 - 654/655), equated with the patrikios Pasagnathes of Theophanes the Confessor, is an Armenian nakharar, famous for resisting the first Arab invasions of Armenia.

Rshtuni is appointed as ishkhan and kouropalates of Byzantine Armenia by Emperor Heraclius when the previous ishkan, David Saharuni, is overthrown by other nakharars.