South Kalimantan is a province of Indonesia. It is the smallest province in Kalimantan, the Indonesian territory of the island of Borneo. The provincial capital was Banjarmasin until 15 February 2022 when it was legally moved to Banjarbaru. The population of South Kalimantan was recorded at just over 3.625 million people at the 2010 Census, and at 4.07 million at the 2020 Census. The official estimate as at mid 2023 was 4,221,929. One of the five Indonesian provinces in Kalimantan, it is bordered by the Makassar Strait in the east, Central Kalimantan in the west and north, the Java Sea in the south, and East Kalimantan in the northeast. The province also includes the island of Pulau Laut, located off the eastern coast of Kalimantan, as well as other smaller offshore islands. The province is divided into 11 regencies and 2 cities. South Kalimantan is the traditional homeland of the Banjar people, although some parts of East Kalimantan and Central Kalimantan are also included in this criterion. Nevertheless, South Kalimantan, especially the former capital city Banjarmasin has always been the cultural capital of Banjarese culture. Many Banjarese have migrated to other parts of Indonesia, as well as neighbouring countries such as Singapore and Malaysia. In addition, other ethnic groups also inhabit the province, such as several groups of the Dayaks, who mostly live in the interior part of the province, as well as the Javanese, who mostly migrated from Java due to the Transmigration program which dated from the Dutch colonial era. It is one of the provinces in Indonesia that has a larger population than Mongolia.

Borneo is the third-largest island in the world, with an area of 748,168 km2 (288,869 sq mi). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda Islands, located north of Java, west of Sulawesi, and east of Sumatra.