The canton of Solothurn or canton of Soleure (German: Kanton Solothurn; Romansh: Chantun Soloturn; French: Canton de Soleure; Italian: Canton Soletta) is a canton of Switzerland. It is located in the northwest of Switzerland. The capital is Solothurn.

The village of Salodurum was founded in the time of the Roman emperor Tiberius (1st century CE). The territory of the canton comprises land acquired by the former town, mainly in the Middle Ages. For that reason the canton is irregular in shape and includes two exclaves along the French border, separated from the rest of the canton by Basel-Landschaft .