Castel San Lorenzo (Cilentan: Castieddu) is a town and comune in the province of Salerno in the Campania region of south-western Italy.

It counts no proper hamlets (frazioni) but several minor localities, that are Annunziata, Concezione, Farneta, Fontana dell'Elice, Galdo, Galloppole, Genzano, Infetina, Insertone, Madonna della Stella, Olivella, Palmento, Parretta, Pianella, Piano della Macchia, Pisciolo, Ponte Calore, Tempa, Tempa delle Monache and Tempa Giardino.

The town of Castel San Lorenzo lies upon a hill above the Calore Lucano river, not too far from the Alburni mountain range.

Italian wine, both red, white and rose, under the Castel San Lorenzo DOC appellation comes from this area.

Grapes destined for DOC production must be harvested up to a maximum yield of 12 tonnes/hectare with the finished wines fermented to a minimum alcohol level of 11.5% for reds and 11% for whites.