Korthio () is a former municipality on the island of Andros, in the Cyclades, Greece. Since the 2011 local government reform it is part of the municipality Andros, of which it is a municipal unit. Its population was 1,706 inhabitants at the 2021 census, and its land area is 81.918 kmò. It shares the island of Andros with the municipal units of Andros and Ydrousa.