Kolijan Rostaq-e Sofla Rural District () is in the Central District of Sari County, Mazandaran province, Iran. Its capital is the village of Sang Tarashan.
At the time of the 2006 National Census, the rural district's population was 16,953 in 4,301 households. There were 21,579 inhabitants in 6,306 households at the following census of 2011. The 2016 census measured the population of the rural district as 21,813 in 6,777 households. The most populous of its 13 villages was Mahdasht, with 4,220 people.