Simplon was a department of the First French Empire. It was named after the Simplon Pass. It was formed in 1810, when the Rhodanic Republic was occupied by the French. Its territory corresponded with that of the present-day Swiss canton of Valais. The capital of Simplon was Sion.
- Sion, cantons: Hérémence, Leuk (French: Loèche), Sierre and Sion.
- Brig, cantons: Brig, Goms (French: Conches), Mörel, Raron and Visp (French: Viège).
- Saint-Maurice, cantons: Entremont, Martigny, Monthey and Saint-Maurice.