Siak River in the context of Riau

Pekanbaru ([pəkanˈbaru]) is the capital city of the Indonesian province of Riau, and a major economic center on the eastern side of Sumatra Island with its name derived from the Malay (Indonesian) word for 'new market' ('pekan' is market and 'baru' is new).It has an area of 632.26 km (244.12 sq mi), with a population of 897,767 at the 2010 Census, and 983,356 at the 2020 Census; the official estimate as at mid 2024 was 1,167,599 (comprising 586,917 males and 580,682 females). It is located on the banks of the Siak River, which flows into the Strait of Malacca, Pekanbaru has direct access to the busy strait and has long been known as a trading port.

A settlement has existed on the site since the 17th century. In the late 19th century, the city was developed to serve the coffee and coal industries, and the Dutch built roads to help ship goods to Singapore and Malacca. This city has an airport called Sultan Syarif Kasim II International Airport, and a port called Sungai Duku that is located by the Siak River.

The Sultanate of Siak Sri Indrapura, often called Sultanate of Siak (Indonesian: Kesultanan Siak Sri Inderapura; Jawi: كسلطانن سياك سري اندراڤور‎), was a kingdom that was located in present-day Siak Regency, and nearby other regions from 1722 to 1949. It was founded by Raja Kecil, who had close relations with the Johor Sultanate, after he failed to seize the Johor throne. The polity expanded in the 18th century to encompass much of eastern Sumatra as it brought various communities under its control through warfare and control of trade between the interior of Sumatra and the Malacca Strait. The Dutch colonial state signed a series of treaties with the Siak rulers in the 19th century, which reduced the area of state influence to the Siak River. For the remainder of the Dutch colonial era, it operated as an independent state with Dutch advisors. After Indonesia's Independence was proclaimed on 17 August 1945, the last sultan of Siak, Sultan Syarif Kasim II, declared his kingdom to join the Republic of Indonesia.