FROSINONE, a town of Italy, in the province of Rome, on the railway between Rome and Naples, about 62 miles from the former and 104 from the latter. It is situated in a rich vine-growing district, at the foot of a hill near the left bank of the Cosa, an affluent of the Sacco or Trerus. Though a place of considerable size and great antiquity, it contains very little of interest either for the classical or mediaeval archaeologist. Its principal buildings are the eight churches and a number of old convents. In the plain below there are some remains of an amphitheatre. Frosinone is easily identified with the ancient Frusino or Frusinum, a city of the Volscians which ultimately became a Roman municipium and received a colony of veterans. Previous to 1870 it was the head of a delegation of the papal states, and as such a place of some importance. The population in 1871 was 10,161.