The Provinces of the Roman Empire from Caesar to Diocletian is a description of all Roman regions during the early imperial period, written by Theodor Mommsen. In separate chapters Mommsen describes the different imperial provinces, each as a stand-alone subject, starting from provinces on the northern frontier of Italy, in Spain, Gallia, Germany, and Britain, then moving east to provinces on the Balkans and in the Middle East, and those in Asia and in Africa.