Aïn Oussera or Aïn Oussara (Arabic: عين وسارة) is a city in Djelfa Province, Algeria, with an estimated (2005) population of 134,174.

This city, located 200 km south of the capital Algiers, is crossed by the Trans-Saharan Highway main road number 1.

The road that runs through the whole of Algeria from north to south over 2000 km, connects Algiers on its southern border with Mali near Tamanrasset.

Ain Oussera, has experienced, since 1990, rapid population growth due to its proximity to the 15 MW Es Salam nuclear reactor.

The nearest airport is the Algerian Air Force's Aïn Oussera airfield (DAAQ).