Castelnuovo di Val di Cecina is a comune (municipality) in the Province of Pisa in the Italian region Tuscany, located about southwest of Florence and about 70 km southeast of Pisa.
Castelnuovo di Val di Cecina borders the following municipalities: Casole d'Elsa, Monterotondo Marittimo, Montieri, Pomarance, Radicondoli, Volterra.
The coat of arms of the municipality of Castelnuovo di Val di Cecina was recognized by D.P.C.M. on 20 April 1954.
The civic flag, granted by D.P.R. on 22 December 1954, is a blue drape.