Valdidentro is a comune (municipality) in the Province of Sondrio in the Italian region Lombardy, located about 140 km northeast of Milan and about 50 km northeast of Sondrio, in the upper Alta Valtellina on the border with Switzerland. It is the seat of hot baths, located on Monte Reit in the frazione of Premadio. Valdidentro borders the following municipalities: Bormio, Grosio, Livigno, Müstair (Switzerland), Poschiavo (Switzerland), Santa Maria Val Müstair (Switzerland), Tschierv (Switzerland), Valdisotto, Zernez (Switzerland).