Sareyn (Persian: سرعين)[a] is a city in the Central District of Sareyn County, Ardabil province, Iran, serving as capital of both the county and the district.

[4] At the time of the 2006 National Census, the city's population was 4,478 in 1,135 households, when it was capital of the former Sareyn District of Ardabil County.

Sareyn was transferred to the new Central District as the county's capital.

[4] The 2016 census measured the population of the city as 5,459 people in 1,582 households.

The population increases to more than 20,000 in the summer because of the many tourists who go there due to the charming climate.