Chah Ab () is a village in Dughayi Rural District of Abkuh District in Quchan County, Razavi Khorasan province, Iran.
At the time of the 2006 National Census, the village's population was 45 in 15 households, when it was in the Central District. The following census in 2011 counted 71 people in 21 households. The 2016 census measured the population of the village as 47 people in 16 households.
In 2020, the rural district was separated from the district in the formation of Abkuh District.