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.