Castiglioncello is a frazione of the comune of Rosignano Marittimo, in the province of Livorno, Tuscany, Italy. It stands on a promontory reaching out into the Ligurian Sea, surrounded by pinewoods and hills that fall right down to the sea forming cliffs, little inlets, coves and sandy beaches. The area was inhabited in Etruscan and Roman times, as attested by the presence of an ancient necropolis. The Medici Grand Dukes of Tuscany had a watch tower built here in the 17th century.