Coat of arms the Riau province, Indonesia

Riau (Jawi: رياو‎) is a province of Indonesia. It is located on the central eastern coast of the island of Sumatra, and extends from the eastern slopes of the Barisan Mountains to the Malacca Strait, including several large islands situated within the Strait. The province shares land borders with North Sumatra to the northwest, West Sumatra to the west, and Jambi to the south, and a maritime border with the Riau Islands and the country of Malaysia to the east. It is the second-largest province in the island of Sumatra after South Sumatra, and is slightly larger than the nation of Jordan. According to the 2020 census, Riau had a population of 6,394,087 across a land area of 89,935.90 km²; the official estimate of population as of mid-2023 was 6,642,874 (comprising 3,398,387 males, which is 51.19% of the total population and 3,246,487 females, which is 48.81% of the total population). The province comprises ten regencies and two cities, with Pekanbaru serving as the capital and largest city. Historically, Riau has been a part of various monarchies before the arrival of European colonial powers. Muara Takus, a Buddhist temple complex believed to be a remnant of the Buddhist empire of Srivijaya c. 11th-12th century, is situated in Kampar Regency in Riau province. Following the spread of Islam in the 14th century, the region was then under control of Malay sultanates of Siak Sri Indrapura, Indragiri, and Johor. The sultanates later became protectorate of the Dutch and were reduced to puppet states of the Dutch East Indies. After the establishment of Indonesia in 1945, Riau belonged to the republic's provinces of Sumatra (1945–1948) and Central Sumatra (1948–1957). On 10 August 1957, the province of Riau was inaugurated and it included the Riau Islands until 2004. Although Riau is predominantly considered the land of Malays, it is a highly diverse province. In addition to Malays constituting one-third of the population, other major ethnic groups include Javanese, Minangkabau, Batak, and Chinese. The local Riau dialect of Malay language is considered as the lingua franca in the province, but Indonesian, the standardised form of Malay is used as the official language and also as the second language of many people. Other than that, different languages such as Minangkabau, Hokkien and varieties of Batak languages are also spoken. Riau is one of the wealthiest provinces in Indonesia and is rich in natural resources, particularly petroleum, natural gas, rubber, palm oil and fibre plantations. Extensive logging and plantation development in has led to a massive decline in forest cover Riau, and associated fires have contributed to haze across the larger region.