Aïn Defla (Arabic: ولاية عين الدفلى, is a wilaya (province) in northern Algeria.

It is located to the southwest of Algiers, the capital.

Localities in Ain Delfa include Aïn Defla, Miliana, El Attaf, Djelida and Djendel.

It is made up of 14 districts and 36 municipalities.

The districts are: The municipalities are: