Sampit is a large town located in East Kotawaringin Regency, Central Kalimantan Province of Indonesia. Previously a timber port town situated on the Sampit River, it has grown to be a medium-sized community with a population of 166,773 according to Statistics Indonesia in 2019, with the economy having since divested from timber products. However, the town is not an autonomous city and is not an administrative division in its own right, despite having a sizeable population and urban built-up.

It consists of ten urban villages (kelurahan) and two "rural" villages (desa), comprising Mentawa Baru Ketapang District (all except 5 desa in the south of the district), and the whole of Baamang District, as detailed below. The total area of the town is 398 square kilometres and the population was estimated at 167,850 as at mid 2024.

In addition, the kelurahan of Mentaya Seberang (administratively part of Seranau District) is situated on the east bank of the Sampit River across from Sampit town ("semerang" in Indonesian means "across" or "on the other side of" [the river]) and covers an area of 253.33 km² with 3,774 inhabitants in 2024 and a postcode of 74324.

The origin of the town's name is disputed. The name is thought to be derived from Chinese. 31 Chinese laborers worked for a plantation in the area during the colonial era, with "sam-it" roughly meaning 31. In the 18th century, sampit is the spelling used by Daniel Beekman in describing the sumpit, a type of blow weapon used by the inhabitants of the Borneo interior.

The region was previously thought to be under a tribal kingdom founded by Ot Danum people between the 13th and 14th century although the existence of the kingdom is disputed. The region became part of the Sultanate of Banjar in the early 16th century. The region was ceded to the Dutch East Indies by Sultan Adam of Banjar on 4 May 1826.

During World War II, Sampit came under control of the Imperial Japanese Navy together with Banjarmasin. The Proclamation of Indonesian Independence was made by Indonesian nationalist in the town through radio and a Japanese newspaper Borneo Shimbun between September and October 1945. Unlike most of cities in Kalimantan which have been liberated by Allied forces of Australia, Sampit remained under Japanese control until 1946. Conflict between Indonesian nationalist and newly arrived Dutch troops continued until 1949.

Sampit became known worldwide following inter-ethnic violent communal clashes between the Dayaks and the Madurese migrants during the Sampit conflict which broke out on 17 February 2001 and lasted for 10 days. There are a number of stories purportedly describing the incident that sparked the violence in 2001. One version claims that it was caused by an arson attack on a Dayak house. Rumours spread that the fire was caused by Madurese, and later a group of Dayaks began burning houses in a Madurese neighbourhood. Another version says that the massacre was triggered by an earlier incident in December 2000 when a Dayak man was killed by three Madurese. The clash was also thought to be triggered by perceived threat of Madurese economically dominating Dayaks, although this is not proven. The conflict has been described by Inside Indonesia as an "ethnic fascism". Central and local government did little to stop the violence and some of the army generals and politicians of Dayak descent decided to use the violence to gain power.

Sampit has a tropical rainforest climate (Af) with heavy rainfall year-round.