Castana is a comune (municipality) in the Province of Pavia, in the Italian region of Lombardy. It is located about 50 kilometres (31 miles) south of Milan and about 20 kilometres (12 miles) southeast of Pavia.
As of 31 December 2004, Castana had a population of 739 and an area of 5.2 square kilometres (2.0 square miles).