Old Latium (Latin: Latium vetus or Latium antiquum) was, in antiquity, the part of the Italian peninsula bounded to the north by the river Tiber, to the east by the central Apennine mountains, to the west by the sea and to the south by Monte Circeo. It covered an area measuring just 50 Roman miles.Mommsen calculated its area at ca. 1,860 square kilometres. It corresponded to the central part of the modern administrative region of Lazio (Italy) and was the traditional territory of the Italic tribe known as the Latins, to which the inhabitants of the archaic city of Rome themselves belonged. Later it was also settled by Rutulians, Volscians, Aequi, and Hernici. It was referred to as "old" (vetus) to distinguish it from the expanded region, denoted Latium by later Romans, that included the region to the south of Old Latium, between Monte Circeo and the river Garigliano - the so-called Latium adiectum ("attached Latium").
Dionysius of Halicarnassus is the main literary source that preserves ancient traditions on the settlement of Latium. In the first book of his Roman Antiquities, Dionysius scrupulously lists and discusses all the legends and traditional stories related by historians or scholars, both Greek and Roman. Other important sources are Pliny the Elder, who in book three of his Natural History gives two lists of the settlements of old Latium, that he says by his time had already disappeared. Livy, Strabo, Festus, and Servius Danielis also provide important information.