Semnan County (Persian: شهرستان سمنان) is a county in Semnan Province in Iran. The capital of the county is Semnan. At the 2006 census, its population (including the portions later split off to form Mehdishahr County and Sorkheh County) was 186,159, in 52,896 families, excluding those portions, the population was 135,872, in 39,128 families. The county has one district (bakhsh): the Central District. The county has one city: Semnan.