San Leo is a comune (municipality) in the Province of Pesaro e Urbino in the Italian region Marche, located about 100 km northwest of Ancona and about 45 km west of Pesaro. As of 31 December 2004, it had a population of 2,955 and an area of 53.3 km².

San Leo borders the following municipalities: Acquaviva (San Marino), Chiesanuova (San Marino), Città di San Marino (San Marino), Maiolo, Montecopiolo, Monte Grimano, Novafeltria, Sassofeltrio, Torriana, Verucchio.

San Leo is home to a large fortress at an altitude of 600 meters above sea level.