Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 475,807.63 km2 (182,812 mi.2), including adjacent islands such as the Simeulue, Nias, Mentawai, Enggano, Riau Islands, Bangka Belitung and Krakatoa archipelago.

The Riau Islands is a province of Indonesia - not to be confused with neighbouring Riau Province from which the islands were separated in 2002. The capital of the province is Tanjung Pinang and the largest city is Batam. It shares a maritime border with Riau and Jambi to the east, Bangka Belitung Islands to the south, Singapore to the northeast, Malaysia and West Kalimantan to the west, and Vietnam and Cambodia to the north. It comprises a total of 1,796 islands scattered between Sumatra, Malay Peninsula, and Borneo including the Riau Archipelago. Situated on one of the world's busiest shipping lanes along the Malacca Strait and the Natuna Sea, the province shares water borders with neighboring countries such as Singapore, Malaysia, and Brunei. The Riau Islands also have relatively large potential mineral resources and energy, as well as marine resources.