Kaj (, also Romanized as Kāj; also known as Gāch Kaj and Qāch Kaj) is a city in the Central District of Ardal County, Chaharmahal and Bakhtiari province, Iran.

At the 2006 census, its population was 3,774 in 800 households, when it was a village in Poshtkuh Rural District. The following census in 2011 counted 4,027 people in 982 households. The latest census in 2016 showed a population of 4,227 people in 1,167 households, by which time Kaj had been elevated to the status of a city. The city is populated by Lurs.

References 

Ardal County

Cities in Chaharmahal and Bakhtiari Province

Luri settlements in Chaharmahal and Bakhtiari Province

Populated places in Ardal County