The largest river system is the Kapuas in West Kalimantan, with a length of . Other major rivers include the Mahakam in East Kalimantan ( long), the Barito, Kahayan, and Mendawai in South Kalimantan (, , and  long respectively), Rajang in Sarawak ( long) and Kinabatangan in Sabah ( long).
The largest river system is the Kapuas in West Kalimantan, measuring . Other significant rivers include the Mahakam in East Kalimantan ( length), the Barito, Kahayan, and Mendawai in South Kalimantan ( lengths), Rajang in Sarawak ( length), and Kinabatangan in Sabah ( length).