Castellino Tanaro (Piedmontese: Castlin Tane) is a comune (municipality) in the Province of Cuneo in the Italian region Piedmont, located about 70 kilometres (43 mi) southeast of Turin and about 35 kilometres (22 mi) east of Cuneo.
Castellino Tanaro borders the following municipalities: Ceva, Igliano, Lesegno, Marsaglia, Niella Tanaro, Roascio, and Rocca Cigliè.
Castellino Tanaro is twinned with: