Bireuën or Bireun is an Indonesian town, the seat of the Bireuën Regency government in the Aceh Special Territory of Sumatra. Bireuen is located at . The town (officially called Kota Juang District) covers an area of 16.91 km<sup>2</sup>, and it had a population of 44,604 at the 2010 Census and 47,670 at the 2020 Census; the official mid-2022 population estimate was 47,983.
Bireuën was once the capital of the Republic of Indonesia in its war of independence. It served as the capital for 1 week.
Bireuën is located in the province of Aceh, a semi-autonomous region in the northern half of Sumatra island. Its location is surrounded by hills which makes it easy to defend.
Bireuen has a tropical rainforest climate (Af) with moderate rainfall from February to September and heavy rainfall from October to January.