Khaf County () is in Razavi Khorasan province, Iran. Its capital is the city of Khaf.
The village of Sedeh was converted to a city in 2021.
At the time of the 2006 National Census, the county's population was 108,964 in 23,896 households. The following census in 2011 counted 121,859 people in 29,923 households. The 2016 census measured the population of the county as 138,972 in 36,399 households.
Khaf County's population history and administrative structure over three consecutive censuses are shown in the following table.
The historical city of Zuzan is located close to Khaf and has been submitted to World Heritage tentative lists by UNESCO.