Poshtkuh Rural District () is in Chahardangeh District of Sari County, Mazandaran province, Iran. Its capital is the village of Telma Darreh.
At the time of the 2006 National Census, the rural district's population was 3,885 in 971 households. There were 3,345 inhabitants in 1,051 households at the following census of 2011. The 2016 census measured the population of the rural district as 3,324 in 1,170 households. The most populous of its 21 villages was Orost, with 709 people.