Castello dell'Acqua is a comune (municipality) in the Province of Sondrio in the Italian region Lombardy , located about 100 kilometres (62 mi) northeast of Milan and about 12 kilometres (7 mi) east of Sondrio. As of 31 December 2004, it had a population of 693 and an area of 13.9 square kilometres (5.4 sq mi).

Castello dell'Acqua borders the following municipalities: Chiuro , Ponte in Valtellina , Teglio .