Borujen County () is in Chaharmahal and Bakhtiari province, Iran. Its capital is the city of Borujen.
The village of Naqneh was converted to a city in 2007.
At the time of the 2006 National Census, the county's population was 113,795, in 27,963 households. The following census in 2011 counted 118,681 people in 32,649 households. The 2016 census measured the population of the county as 122,483, in 36,238 households.
Borujen County's population history and administrative structure over three consecutive censuses are shown in the following table.