Mekarsari is a location situated within the Barito Kuala Regency in the Indonesian province of South Kalimantan. The regency occupies an area of 2,425.83 km2 in the southwestern portion of the province.
The region is geographically defined by its proximity to the lower reaches of the Barito River, which separates it from Banjarmasin city and other surrounding regencies to the east. It shares a western border with the Central Kalimantan province.