West Kalimantan is a province of Indonesia. It is one of five Indonesian provinces comprising Kalimantan, the Indonesian part of the island of Borneo. Its capital and largest city is Pontianak. It is bordered by East Kalimantan and Central Kalimantan to the east, the Malaysian state of Sarawak to the north, and the Pacific Ocean to the west and the Java Sea to the south. The province has an area of 147,037 km2, and had a population of 4,395,983 at the 2010 Census and 5,414,390 at the 2020 Census; the official estimate as at mid 2023 was 5,623,328. Ethnic groups include the Dayak, Malay, Chinese, Javanese, Bugis, and Madurese. The borders of West Kalimantan roughly trace the mountain ranges surrounding the vast watershed of the Kapuas River, which drains most of the province. The province shares land borders with Central Kalimantan to the southeast, East Kalimantan to the east, and the Malaysian territory of Sarawak to the north.

East Kalimantan is a province of Indonesia. Its territory comprises the eastern portion of Borneo. It had a population of about 3.03 million at the 2010 census, 3.42 million at the 2015 census, and 3.766 million at the 2020 census; the official estimate as at mid 2023 was 4,030,488. Its capital is the city of Samarinda.