Kotawaringin is a location in Indonesia situated on the south coast of Borneo. Historically, it existed as the Kotawaringin Sultanate, which encompassed territory that currently makes up the western portion of the Indonesian province of Central Kalimantan.
The sultanate's capital was the historic town of Waringin, located on the east bank of the Lamandau River to the northwest of Pangkalan Bun. Between 1949 and 1950, the area functioned briefly as an autonomous "native state" within the United States of Indonesia.
Following this period, Kotawaringin was formally established as a separate regency within the Province of South Kalimantan. On June 26, 1959, the Kotawaringin Regency was divided into two distinct administrative areas: West Kotawaringin Regency and East Kotawaringin Regency.