Shirin Su District () is in Maneh County, North Khorasan province, Iran. Its capital is the village of Khartut, whose population at the time of the 2016 National Census was 703 in 164 households.
In 2023, Maneh District was separated from Maneh and Samalqan County in the establishment of Maneh County and renamed the Central District. The new county was divided into two districts of two rural districts each, with Pish Qaleh as its capital and only city at the time.