It was separated from Lucania on the north by a line drawn from the mouth of the river Laus on the west to a point a little south of the river Crathis on the east.
Augustus joined it with Lucania (from which it was divided by the rivers Laus and Crathis) to form the third region of Italy.
The precise limits were the river Silarus on the north-west, which separated it from Campania, and the Bradanus, which flows into the Gulf of Tarentum, on the north-east; while the two little rivers Laus and Crathis, flowing from the ridge of the Apennines to the sea on the west and east, marked the limits of the district on the side of the Bruttii.
The Crathis, which forms at its mouth the southern limit of the province, belongs almost wholly to the territory of the Bruttii, but it receives a tributary, the Sybaris (Coscile), from the mountains of Lucania.
At the narrowest point the plain of Sibari, through which the rivers Coscile (Sybaris) and Crati (Crathis) flow to the sea, occurs on the east coast, extending halfway across the peninsula.