Kittanning is a borough in and the county seat of Armstrong County, Pennsylvania, United States. It is situated 36 miles northeast of Pittsburgh, along the east bank of the Allegheny River. The population was 3,921 at the 2020 census. The name is derived from Kithanink, which means 'on the main river' in Lenape or the Delaware language, from kit- 'big'+ hane 'mountain river'+-ink. "The main river" is a Lenape term for the Allegheny and Ohio combined, which they considered as all one river.