Bir el Ater (Arabic: بئر العاتر) is a city located in far eastern Algeria.

There are deposits of Djebel Onk Phosphates, the largest in Algeria which are extracted and shipped by train to Annaba a port, 300 km north on the Mediterranean or are used locally.

A few kilometers north of Bir el-Ater are the ruins of a large Roman oil mill, preserved on two floors.

The name of the village in antiquity was Vicus Aterii indicating only a small settlement, though it was the seat of an ancient Christian bishopric in the Roman province of Byzacena.

[3][4] The ancient Bishopric survives today as a titular see of the Roman Catholic Church called Vicus Aterii.