| Mehdishahr County | |
| Native Name: | Persian: شهرستان مهدیشهر |
| Settlement Type: | County |
| Image Map1: | IranSemnan-SVG.svg |
| Map Caption1: | Location of Semnan province in Iran |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Name1: | Semnan |
| Seat Type: | Capital |
| Seat: | Mehdishahr |
| Parts Type: | Districts |
| Parts Style: | para |
| P1: | Central |
| P2: | Shahmirzad |
| Population As Of: | 2016 |
| Population Total: | 47475 |
| Coordinates: | 35.8644°N 53.4444°W |
| Coordinates Footnotes: | [1] |
| Timezone: | IRST |
| Utc Offset: | +3:30 |
Mehdishahr County (Persian: شهرستان مهدیشهر) is in Semnan province, Iran. Its capital is the city of Mehdishahr.[2]
After the 2006 National Census, Mehdishahr District was separated from Semnan County in the establishment of Mehdishahr County, which was divided into two districts and three rural districts, with Mehdishahr as its capital.[2]
At the time of the 2011 census, the county's population was 41,896 people in 11,997 households.[3] The 2016 census measured the population of the county as 47,475 in 15,226 households.[4]
Mehdishahr County's population history and administrative structure over two consecutive censuses are shown in the following table.
| Administrative Divisions | 2011 | 2016 | |
|---|---|---|---|
| Central District | 25,114 | 30,781 | |
| 296 | 299 | ||
| Darjazin (city) | 4,964 | 5,997 | |
| Mehdishahr (city) | 19,854 | 24,485 | |
| Shahmirzad District | 16,782 | 16,694 | |
| 2,183 | 1,659 | ||
| 5,717 | 3,844 | ||
| Shahmirzad (city) | 8,882 | 11,191 | |
| Total | 41,896 | 47,475 | |