Siak Regency

Siak (Jawi: سياك‎), is a regency (kabupaten) of Riau Province, on the island of Sumatra, Indonesia. It has an area of 8,556.09 km² and had a population of 376,742 at the 2010 Census and 457,940 at the 2020 Census; the official estimate as at mid 2024 was 495,760, comprising 254,501 males and 241,259 females. The administrative centre of the regency is located at Siak Sri Indrapura in Mempura District . The northern part of this regency contains a large part of the Bukit Batu Biosphere Reserve.

Previously the area was part of the Sultanate of Siak Sri Indrapura. At the beginning of the independence of Indonesia, Sultan Syarif Kasim II, the Sultanate of Siak was the last state to join the Republic of Indonesia. Later this region was included in an area under the Siak Kewedanan Bengkalis. On 4 October 1999 under Law No. 53 of 1999, a Siak Regency was established from what had previously been the southern districts of Bengkalis Regency, and Siak Sri Indrapura was declared the administrative capital of Siak Regency.