Castelnuovo Cilento (Cilentan: Castiedde Nuove) is a town and comune in the province of Salerno in the Campania region of south-western Italy.

The medieval village of Castelnuovo was part of the fief of the Agnello family from Senerchia.

The current toponym, adding Cilento, was adopted in 1861, after the Italian unification.

The municipality borders with Ascea, Casal Velino, Ceraso, Salento and Vallo della Lucania.

The territory of Castelnuovo is served by a pair of railway stations, Vallo della Lucania-Castelnuovo and Casal Velino, both on the Naples-Reggio Calabria line.