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.

Theodor Mommsen (1817-1903) was a German classical scholar, historian, jurist, journalist, politician and archaeologist. He was one of the greatest classicists of the 19th century. His work regarding Roman history is still of fundamental importance for contemporary research. He received the Nobel Prize in Literature in 1902 for his monumental work, The History of Rome. He was also a prominent German politician, as a member of the Prussian and German parliaments. His works on Roman law and on the law of obligations had a significant impact on the German civil code.