Banjarmasin is a city and the capital of South Kalimantan, Indonesia. It is located on a delta island near the junction of the Barito and Martapura rivers. Historically the center of Banjarese culture and the capital of the Sultanate of Banjar, it is the biggest city in South Kalimantan and one of main cities of Kalimantan. The city covers an area of 98.46 square kilometres (38.02 sq mi) and had an estimated population of 657,663 in 2020. Greater Banjarmasin, also known as Banjarbakula, is an urban agglomeration of around two million people covering an area of 8,136 square kilometres (3,141 sq mi), which includes Banjarbaru, parts of Banjar Regency, Barito Kuala Regency, and Tanah Laut Regency and accounts for almost half of the province's population. It is the third most populous city on the island of Borneo after Samarinda and Balikpapan, and the most populous officially recognized metropolitan area on the entire island with more than three times the population of Kuching metropolitan area, the second largest officially recognized metropolitan area in the island.

It is the de jure seat of the South Kalimantan governor although some of provincial buildings have been relocated to Banjarbaru and also location of provincial parliament. It is the only officially recognized metropolitan area located in Kalimantan as of 2019.