Castelletto is a residential quarter of Genoa, north-western Italy. It occupies a hilly area which, until the 17th century, it was outside the city walls.
The quarter is included in the city's Municipio I Centro Est and includes three urban units ., they had a total population of 28,857. The name, meaning "small castle" in Italian, stems from a fort commanding the whole Genoese area, known since as early as the 10th century AD and dismantled in the late 19th century.