The Kapuas River (or Kapoeas River) is a river in the Indonesian part of Borneo island, at the geographic center of Maritime Southeast Asia. At 1,143 kilometers (710 mi) in length, it is the longest river of Indonesia[1][2] and one of the world's longest island rivers.[3] It originates in the Müller mountain range at the center of the island and flows west into the South China Sea creating an extended marshy delta. The delta is located west-southwest of Pontianak, the capital of West Kalimantan province.[4] This Kapuas River should be distinguished from another Kapuas River, which starts on the other side of the same mountain range in central Borneo, but flows to the south, merging with the Barito River and discharging into the Java Sea.