The province of Sondrio (Italian: provincia di Sondrio), also known as Valtellina (the major valley of the province) is a province in the Lombardy region of Italy. Its provincial capital is the city of Sondrio.

As of 2024, it has a population of 179,165.

The province was established in 1815, within the Kingdom of Lombardy–Venetia, combining the valleys of Valtellina, Valchiavenna and Bormio .

Before the Roman conquest, the territory was inhabited by Celts (Lepontii) and Rhaetians (Camunni). The Romans included this area in their Cisalpine Gaul province.