The Seduni or Sedunii were a Gallic tribe in the valley of the Upper Rhone at Roman contact, whom Julius Caesar (B. G. iii. 1, 7) mentions: Nantuates Sedunos Veragrosque. These tribes were conquered by Rome are also mentioned in the Trophy of the Alps (Plin. iii. 20) in the same order. They were east of the Veragri, in the modern Swiss canton of Valais. Their chief town was Sedunum (modern Sion, Switzerland). The Seduni also participated in the Battle of Octodurus at the site of modern-day Martigny, Switzerland.