Fondi has an ancient history, dating back to around 1000 BC and its first settlements. Later, the area was settled by the Italic tribes of Aurunci and later with Volsci.
The first historical references to Fondi date back to the year 338 BC, during the Latin War, when its inhabitants gained minor Roman citizenship status. After an unsuccessful attempt of revolt in 330 BC, Fondi remained a Roman prefecture. In 188 BC, Fondi received full city status.
The historical importance of Fondi lays in its position across the old Via Appia. Since 312 BC, it was for more than two millennia the main roadway from Rome to southern Italy.
After the Gothic War and the Lombard conquest of Italy, the city remained a dominion of the Eastern Roman Empire. Later a part of the Papal States was burnt out by the Saracens. Fondi was then passed to the Duchy of Gaeta.
In 1140 Fondi was granted to the Dell'Aquila family. But in 1299 it passed to the powerful Caetani barons. More precisely in the person of Loffredo Caetani, nephew of Pope Boniface VIII. For two centuries he made Fondi the centre of their power, as well as a hub of artistic development.
The Caetani lost Fondi after Charles VIII of France 's expedition to southern Italy. Fondi was assigned to the Prospero Colonna. During this period, Fondi entered another period of artistic and cultural splendour, thanks also to the court held by Giulia Gongoza, who lived in the town between 1526-34.
Fondi was sacked by Barbarossa in 1534. He was seeking to kidnap the beautiful Giulia and bring her as a gift to his emperor Suleiman, but she managed to escape.
Another sacking then took place in 1594 which triggered the decline of Fondi. The city was acquired by the di Sangro family in 1720.
In 1818 the already declining Fondi went through a malaria epidemic and the city lost the bishopric seat existing there since the very early years of Christianity.