Riau is a province of Indonesia, located in the centre and eastern coast of Sumatra along the Strait of Malacca. Until 2004 the province included the offshore Riau Islands, a large group of small islands (of which the principal islands are Batam and Bintan) located east of Sumatra Island and south of Singapore, before these islands were split off as Riau Islands Province in July 2004. The provincial capital of Riau Province and its largest city is Pekanbaru. Other major cities include Dumai, Selat Panjang, Bagansiapiapi, Bengkalis, Bangkinang, Rengat and Siak Sri Indrapura.

Riau is currently one of the richest provinces in Indonesia and is rich with natural resources, particularly petroleum, natural gas, rubber, palm oil and fiber plantations. However extensive logging has led to a massive decline in forest cover from 78% in 1982 to only 33% in 2005. This has been further reduced an average of 160,000 hectares per year on average, leaving 22%, or 2.45 million hectares left as of 2009. Deforestation for palm oil and paper has led to not only perennial serious haze over the province, but in Kuala Lumpur, Malaysia, and intensifying flooding and landslides. Kuala Lumpur and surrounds has been sent into "unhealthy" air quality levels again in mid 2012 from Indonesian haze originating in Riau.

Since the 1970s, much of Indonesia has experienced declining population growth rates. Riau has been a significant exception, with increasing rates every decade since 1970 to a 4.35 percent annual rise for the 1990s. The provincial population is 5,543,031 (as at the 2010 census).