Kusaj () is a village in Qaleh Darrehsi Rural District of the Central District in Maku County, West Azerbaijan province, Iran.
At the time of the 2006 National Census, the village's population (as Kuseh Kandi) was 425 in 87 households. The following census in 2011 counted 378 people in 103 households, by which time the village was listed as Kusaj. The 2016 census measured the population of the village as 375 people in 121 households.