Sundergarh District, also spelled Sundergarh District, is a district in the northwestern part of Odisha state in eastern India. Sundergarh district is bound by Raigarh district of Chhattisgarh in the west, Jashpur district of Chhattisgarh in the North-West, Simdega district of Jharkhand in the North, West Singhbhum district of Jharkhand and Keonjhar district of Odisha in the east and Jharsuguda, Sambalpur, Deogarh and Angul districts of Odisha in the South. The town of Sundergarh is the district headquarters.

Sundergarh district forms the North western part of Odisha state and is the Second largest district in the state accounting for 6.23% of the total area. Geographical Area of the district is 9712 km2. The district spreads from 21°36′N to 22°32′N and from 83°32′E to 85°22′E.

Two princely States of Gangpur and Bonaigarh constitute the present district of Sundergarh, consequent upon merger of the princely States on 1 January 1948. It is understood that, in ancient times, this district was under the rulers of different dynasties. However, divergent views are available regarding the origin of the ruling family. Bonaigarh was known as Bonai Mandala and was ruled by Mayura dynasty as a feudetory of Bhoumakara dynasty of Toshali. The present royal family of Gangpur belongs to the Parmar dynasty and Bonaigarh belongs to Kadamba dynasty. These ex-states were under the suzerainty of Sambalpur which formed part of the dominion of the Maratha Rajas of Nagpur. They were ceded to the British Government in 1803 by the Maratha Chief Raghuji Bhonsla of Nagpur under the treaty of Deogaon(near Rourkela). But they were restored to him by special engagement in 1806. They were finally ceded in 1826. In 1905, these two Odia princely states were transferred from the control of the Commissioner of Chhotanagpur to that of Odisha Division and a separate Political Agent was appointed.

According to the 2011 census Sundergarh district has a population of 2,080,664, roughly equal to the nation of Macedonia or the US state of New Mexico.This gives it a ranking of 221st in India (out of a total of 640).The district has a population density of 214 inhabitants per square kilometre (550/sq mi).Its population growth rate over the decade 2001–2011 was 13.66%.Sundargarh has a sex ratio of 971 females for every 1000 males, and a literacy rate of 74.13%.