| Castel d'Ario | |
| Official Name: | Comune di Castel d'Ario |
| Coordinates: | 45.1833°N 69°W |
| Region: | Lombardy |
| Province: | Mantua (MN) |
| Frazioni: | Gazzuolo I, Gazzuolo II, Madonnina, Roppi, Susano, Villa, Villagrossa |
| Mayor: | Daniela Castro |
| Area Total Km2: | 22.58 |
| Population Total: | 4635 |
| Population As Of: | 31 May 2017[1] |
| Population Demonym: | Casteldariesi |
| Elevation M: | 24 |
| Postal Code: | 46033 |
| Area Code: | 0376 |
Castel d'Ario (Mantovano: Castlar) is a comune (municipality) in the Province of Mantua in the Italian region Lombardy, located about 150km (90miles) east of Milan and about 15km (09miles) east of Mantua. It was the birthplace of race car driver Tazio Nuvolari.
Castel d'Ario borders the following municipalities: Bigarello, Roncoferraro, Sorgà, Villimpenta.