Ferentino is a town and comune in Italy, in the province of Frosinone, Lazio, 65 kilometres (40 mi) southeast of Rome.

Strong in textiles (linen and embroidery) and handicraft (clay bricks from Fornaci Giorgi), after World War II Ferentino experienced a heavy industrial growth, mainly in pharmaceuticals.

[3] The Cathedral of Sts John and Paul occupies a part of the level top of the ancient acropolis; it was reconstructed on the site of an older church in 1099–1118; the interior was modernized in 1693, but was restored to its original form in 1902.

The Gothic church of Santa Maria Maggiore, in the lower town (13th-14th century), has a very fine exterior; the interior, the plan of which is a perfect rectangle, has been spoiled by restoration.

In 2021, Italy's Minister of Culture awarded €1.5 million to fund the first full excavation of the town's Roman theatre, which will be partially restored for community use.