| Castelletto Merli | |
| Official Name: | Comune di Castelletto Merli |
| Coordinates: | 45.0667°N 22°W |
| Region: | Piedmont |
| Province: | Alessandria (AL) |
| Frazioni: | Borgo San Giuseppe, Case Bertana, Cosso, Costamezzana, Godio, Guazzolo, Perno Inferiore, Perno Superiore, Sogliano, Terfengato, Terfengo, Valle |
| Mayor: | Ivan Cassone |
| Area Total Km2: | 11.8 |
| Population Footnotes: | [1] |
| Population Total: | 388 |
| Population As Of: | 31 July 2014 |
| Population Demonym: | Castellettesi |
| Elevation M: | 268 |
| Postal Code: | 15020 |
| Area Code: | 0141 |
Castelletto Merli is a comune (municipality) in the Province of Alessandria in the Italian region Piedmont, located about 40km (30miles) east of Turin and about 35km (22miles) northwest of Alessandria.
Castelletto Merli borders the following municipalities: Alfiano Natta, Cerrina Monferrato, Mombello Monferrato, Moncalvo, Odalengo Piccolo, and Ponzano Monferrato.