Esfarayen County () is in North Khorasan province, Iran. Its capital is the city of Esfarayen.
In 2023, Daman Kuh and Zorqabad Rural Districts were separated from the Central District in the formation of Zorqabad District. Bam and Safiabad District was separated from the county in the establishment of Bam and Safiabad County and renamed the Central District.
At the time of the 2006 National Census, the county's population was 119,152 in 30,307 households. The following census in 2011 counted 127,012 people in 35,903 households. The 2016 census measured the population of the county as 120,513 in 36,519 households.
Esfarayen County's population history and administrative structure over three consecutive censuses are shown in the following table.