Avaj (, also Romanized as Avej; also known as Aveh) is a city in and capital of Avaj District, in Buin Zahra County, Qazvin Province, Iran. At the 2006 census its population was 3,695, in 1,042 families.
Avaj lies west of Tehran along Road 37, about 20 kilometres south by road from Abgarm. It is located in Qazvin province and has an estimated population of 3,600. It lies in an agricultural area. Avaj was near the epicenter of the 2002 Bou'in-Zahra earthquake and thus was severely affected by it, with roughly half the town being razed.