San Colombano al Lambro is a comune in the Metropolitan City of Milan, in the Italian region of Lombardy, located about 40 kilometres southeast of Milan. San Colombano al Lambro is an exclave of the province of Milan at the junction between the Pavia and Lodi provinces. The exclave arose when the province of Lodi was carved out of the province of Milan, but a referendum in San Colombano indicated the locals' wish to stay in Milan.