Aarau District is a district in the Swiss Canton of Aargau with administrative capital Aarau encompasses the agglomeration of Aarau south of the Juras.

In 2009, the Aargau District had a total area of 104.48 square kilometers (40.34 sq mi). Of that area, 32.06 km2 (12.38 sq mi), or about 30.7%, was cultivated land, 50.38 km2 (19.45 sq mi), or about 48.2%, was forested and 21.02 km2 (8.12 sq mi), or about 20.1%, has some type of construction on it.

In December 2018, Aarau District had a population of 80,309.

In 2000, there were 3,277 homes with 1 or 2 persons in the household, 14,181 homes with 3 or 4 persons in the household, and 9,295 homes with 5 or more persons in the household. The average number of people per household was 2.24 individuals.