Val Masino (Western Lombard: Val Màsen) is a comune (municipality) in the Province of Sondrio in the Italian region Lombardy , located about 90 kilometres (56 mi) northeast of Milan and about 20 kilometres (12 mi) northwest of Sondrio, on the border with Switzerland. As of 31 December 2004, it had a population of 962 and an area of 116.0 square kilometres (44.8 sq mi).

Val Masino and Val Di Mello are one of the most renowned areas for all climbing disciplines (Sportsclimbing, trad multipitching, bouldering and alpinism). It has become famous internationally through the Melloblocco bouldering festival, which brings together thousands of climbers from all over the world.

The municipality of Val Masino contains the frazioni (subdivisions, mainly villages and hamlets) Bagni del Masino, Case Sparse, Cataeggio, Filorera, Piana, San Martino, Visido di Fuori.

Val Masino borders the following municipalities: Ardenno , Bondo (Switzerland), Buglio in Monte , Chiesa in Valmalenco , Civo , Novate Mezzola , Stampa (Switzerland), Vicosoprano (Switzerland).