Grosio is a comune in the Province of Sondrio in the Italian region of Lombardy, located about 130 kilometres northeast of Milan and about 35 kilometres northeast of Sondrio, on the border with Switzerland. The municipality of Grosio contains the frazioni Tiolo, Vernuga and Ravoledo. Grosio borders the following municipalities: Grosotto, Monno, Poschiavo, Sondalo, Valdidentro, Valdisotto, Vezza d'Oglio.