Sepidar Rural District () is in Armand District of Khanmirza County, Chaharmahal and Bakhtiari province, Iran. Its capital is the village of Shahrak-e Sunk, whose population at the time of the 2016 National Census was 1,602 people in 392 households.
In 2019, Armand Rural District and Khanmirza District were separated from Lordegan County in the establishment of Khanmirza County, and Sepidar Rural District was created in the new Armand District.