East Kotawaringin Regency () is one of the thirteen regencies which comprise the Central Kalimantan Province on the island of Kalimantan (Borneo), Indonesia. It originally covered a much larger part of the province, having been split from a single Kotawaringin Regency on 26 June 1959 into separate regencies for East and West Kotawaringin, but on 10 April 2002 several districts in the west of the regency were split off to form the new Seruyan Regency, and several districts in the east of the regency were similarly split off to form the new Katingan Regency. The area of the residual East Kotawaringin Regency is 15,541.75 km<sup>2</sup>, and its population was 374,175 at the 2010 Census, and 428,900 at the 2020 Census; the official estimate as at mid 2024 was 448,180 (comprising 231,400 males and 216,780 females). The town of Sampit is the capital of East Kotawaringin Regency.
The residual regency is essentially the catchment area of the Mentaya (Sampit) River. The large town of Sampit (the administrative centre of the regency) lies on the west bank of the river; its metropolitan area encompasses most of Mentawa Baru Ketapang District (except 5 rural desa in the south) and all of Baamang District, plus a part of Seranau District.
At the 2010 Census, East Kotawaringin Regency consisted of fifteen districts (kecamatan), but two more districts (Tualan Hulu and Telaga Antang) were subsequently established by the splitting of existing districts. The seventeen districts are tabulated below with their areas and population totals from the 2010 Census and the 2020 Census, together with the official estimates as at mid 2024. The table also includes the locations of the district administrative centres, the number of administrative villages in each district (totaling 168 rural desa and 17 urban kelurahan), and its postal codes.
Notes: (a) comprises 2 kelurahan (Samuda Kota and Basirih Hilir) and 8 desa. (b) comprises 5 kelurahan (Ketapang, Mentawa Baru Hilir, Mentawa Baru Hulu, Pasir Putih and Sawahan) and 6 desa. <br>(c) including one kelurahan (the district admin centre). (d) except for the village of Mentaya Seberang, which has a post code of 74324. <br>(e) comprises 5 kelurahan (Baamang Barat, Baamang Hilir, Baamang Hulu, Baamang Tengah and Tanah Mas) and 1 desa (Tinduk), which are all part of Greater Sampit. <br>(f) comprises 2 kelurahan (Kota Besi Hilir and Kota Besi Hulu) and 9 desa. <br>(g) the 2010 population of Tualan Hulu District is included in the figures for the districts from which it was cut out. <br>(h) the 2010 population of Telaga Antang District is included in the figure for Antang Kalang District. <br>(i) except for the village of Buana Mustika, which has a post code of 74356.