An ancient city of the Aurunci, which became a Roman municipium in 188 BC, Fondi was important in the Middle Ages and already in the 5th century was part of the territory of the Church. Destroyed by the Saracens (844), in 1266 it was conquered by Manfredi. In the 14th century it passed to the Caetani, becoming the center of their power. Indeed, with the favor of Onorato I Caetani, on 20 September 1378 the French cardinals were able to elect at Fondi the antipope Clement VII. Although it is not to be excluded that a Christian community existed in Fondi in the 3rd century, given the dubious reliability of those manuscripts of the *Liber Pontificalis* which state that a bishop of Fondi was consecrated by Pope Anterus (235-36), and the lack of certainty that the martyr Magnus was a local bishop, the first certain prelate is Vitalis, who participated in the Synod of Rome from 487 to 502. Among the bishops of the see should be noted St. Andrew, mentioned by St. Gregory the Great (Dial., 3, 7), and Gennaro Vincenzo Tortora, with whom the series ended when Pius VII, on 27 June 1818, united the diocese of Fondi with the neighboring diocese of Gaeta.
Fondi still preserves the walls of the 1st century BC, with a polygonal section; the ancient Appian Way, crossing it from east to west, constitutes its decumanus. Notable are the former cathedral of St. Peter, with its ambo and episcopal chair of Campanian art from the 12th and 13th centuries; the bell tower of St. Mary, the interior of St. Francis, and the cloister of St. Dominic from the 14th century; the collegiate church of St. Mary, the portal of St. Francis; the fortress and the feudal palace from the 15th century. - See pl. XCIV.