| Borgo San Siro | |
| Official Name: | Comune di Borgo San Siro |
| Native Name: | Bùrgh San Sir |
| Coordinates: | 45.25°N 11°W |
| Region: | Lombardy |
| Province: | Pavia (PV) |
| Frazioni: | Torrazza |
| Mayor: | Antonio Ballottin |
| Area Total Km2: | 17.64 |
| Population Total: | 953 |
| Population As Of: | 31 December 2021[1] |
| Population Demonym: | Borghigiani |
| Elevation M: | 98 |
| Postal Code: | 27020 |
| Area Code: | 0382 |
Borgo San Siro (Western Lombard: Bùrgh San Sir) is a comune (municipality) in the Province of Pavia in the Italian region Lombardy, located about 25km (16miles) southwest of Milan and about 12km (07miles) northwest of Pavia, in the western Lomellina.
Borgo San Siro borders the following municipalities: Bereguardo, Gambolò, Garlasco, Tromello, Vigevano, Zerbolò.