The province of Frosinone is a province in the Lazio region of Italy. Its capital is the city of Frosinone. It has an area of 3,247 square kilomet…The province of Frosinone is a province in the Lazio region of Italy. Its capital is the city of Frosinone. It has an area of 3,247 square kilometres and a total population of 493,605. The province contains 91 comuni, listed in the comuni of the province of Frosinone.