Khomeynishahr County () is in Isfahan province, Iran. Its capital is the city of Khomeynishahr.
After the 2011 National Census, the village of Asgharabad was elevated to the status of a city.
At the time of the 2006 census, the county's population was 282,888 in 57,551 households. The following census in 2011 counted 311,629 people in 90,715 households. The 2016 census measured the population of the county as 319,727 in 98,269 households.
Khomeynishahr County's population history and administrative structure over three consecutive censuses are shown in the following table.