Sedeh District () is in Qaen County, South Khorasan province, Iran. Its capital is the city of Arianshahr.
At the time of the 2006 National Census, the district's population was 18,792 in 5,155 households. The following census in 2011 counted 20,482 people in 6,034 households. The 2016 census measured the population of the district as 22,473 inhabitants in 6,909 households.