Khondab (Persian: خنداب is a city in the Central District of Khondab County, Markazi province, Iran, serving as capital of both the county and the district. It is also the administrative center for Khondab Rural District. The heavy water reactor IR-40 is nearby.

At the 2006 National Census, its population was 6,982 in 1,787 households, when it was in the former Khondab District of Arak County. The following census in 2011 counted 7,753 people in 2,186 households, by which time the district had been separated from the county in the establishment of Khondab County. The latest census in 2016 showed a population of 7,810 people in 2,358 households.