ARRETUM, (Cicero, Cæsar); Arretium, (Ptolemy); Urbs Arretinorum, (Polybius); one of the twelve ancient towns of Tuscany, near the Arnis and Clanis, situated in a pleasant valley. Now Arenzo, 42 miles east of Florence. E. Long. 13. 18. Lat. 43. 15.