Harsin County (Persian: شهرستان هرسین) is in Kermanshah province, Iran. Its capital is the city of Harsin, 44 kilometres (27 mi) east of Kermanshah, 1,570 metres (5,150 ft) above sea level.

The population is Kurdish and Shi'ite.

At the time of the 2006 National Census, the county's population was 90,452 in 20,788 households. The following census in 2011 counted 86,342 people in 23,176 households. The 2016 census measured the population of the county as 78,350 in 22,506 households.

Harsin County's population history and administrative structure over three consecutive censuses are shown in the following table.

The county is bounded to the north by Sahneh County, to the south by Khorramabad County in Lorestan province, to the east by Nahavand County in Hamadan province and to the west by Kermanshah County.

Attractions of the county include the Essaqwand Rock Tombs and the Behistun Inscription.

Media related to Harsin County at Wikimedia Commons