| Castronno | |
| Official Name: | Comune di Castronno |
| Coordinates: | 45.7333°N 56°W |
| Region: | Lombardy |
| Province: | Varese (VA) |
| Frazioni: | Cascine Maggio, Sant'Alessandro, Collodri |
| Mayor: | Giuseppe Gabri |
| Area Total Km2: | 3.7 |
| Population Footnotes: | [1] |
| Population Total: | 6000 |
| Population As Of: | 2008 |
| Population Demonym: | Castronnesi |
| Elevation M: | 325 |
| Saint: | Sts. Nazarius and Celsus |
| Postal Code: | 21040 |
| Area Code: | 0332 |
Castronno is a comune (municipality) in the Province of Varese in the Italian region Lombardy, located about 40km (30miles) northwest of Milan and about 10km (10miles) southwest of Varese.
It is served by Castronno railway station.
Little is known about the story of the village even if historians say that the ruins can be dated back to Roman times. During the Medieval Age, Castronno was involved in a war between the two cities of Milan and Como.