The Central District of Mehdishahr County () is in Semnan province, Iran. Its capital is the city of Mehdishahr.
In 2007, 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.
At the time of the 2011 National Census, the district's population was 25,114 people in 7,105 households. The 2016 census measured the population of the district as 30,781 inhabitants in 9,531 households.