Aslan Duz (Persian: اصلاندوز) is a city in the Central District of Aslan Duz County, Ardabil province, Iran, serving as the capital of both the county and the district. The Battle of Aslanduz was fought nearby in 1812.

At the 2006 census, its population was 3,910 in 862 households, when it was in the former Aslan Duz District of Parsabad County. The following census in 2011 counted 4,557 people in 1,172 households. The census in 2016 showed a population of 6,348 people in 1,760 households.

In 2017, the district was separated from the county in the establishment of Aslan Duz County, which was divided into two districts of two rural districts each, with Aslan Duz as its capital and only city.