Dun Sar () is a village in Gatab-e Shomali Rural District of Gatab District in Babol County, Mazandaran province, Iran.
At the time of the 2006 National Census, the village's population was 1,776 in 456 households. The following census in 2011 counted 1,725 people in 507 households. The 2016 census measured the population of the village as 1,477 people in 492 households.