Thénia (الثنية), sometimes written as Thenia, with around 40,000 inhabitants, is the chief town in the daïra of the same name, in the wilaya of Boumerdès, in northern Algeria. Historically, the name is a contraction of Theniet Beni Aicha (ثنية بني عائشة) "the mountain pass of the sons of Aisha", the Arabic translation of the Kabyle Berber toponym Tizi n At Ɛica. The steep-sided pass, which is only about 800 metres wide at its narrowest point, is sometimes taken to mark the transition between Mitidja and Grande Kabylie.