At the end of the third century CE, the Emperor Diocletian divides the great Roman province of Africa Proconsularis into three smaller provinces: Zeugitana in the north, still governed by a proconsul and referred to as Proconsularis, Byzacena, and Tripolitania in the south.

It corresponds roughly to the modern Tunisian region of Sahel.Hadrumetum (modern Sousse) becomes the capital of the newly made province, whose governor has the rank of consularis.

At this period the metropolis of Byzacena is, after Carthage, the most important town in Roman Africa.