Historically, Keonjhar was a princely state before merging into Odisha. It is believed that it was the part of Khijjinga territory. In the first half of the 12th century A.D, it emerged as a separate state under the kingship of Jyoti Bhanja. It has been prove that the then State of Keonjhar consisted of only the northern half of the modern district for a long period of time before the emergence of Jyoti nja as King. During the last part of the 15th century the southern half went into the hands of King Govinda Bhanja under whose reign the place of Keonjhar was extended from Singhbhum in the north to Sukinda (A Zamindari in Cuttack district) in the South and from Mayurbhanj State in the East to the borders of the States of Bonai, Pal Lahara and Anugul in the West. When there was the rule of Pratap Balabhadra Bhanja (1764-1792 A.D.) at that time two small areas of Tillo and Jujhpada were purchased from the Zamindar of Kantajhari and then added to the state. Later, these were recognised as the parts of Keonjhar in the Sanad granted by the East India Company to Raja Janardan Bhanj in the year 1804. Since then there had been no territorial changes of the State till its merger with the Province of Orissa.
Geographically, the district has a total 8,303 sq kms. area and occupies the rank 4th in State and 91st in India on the bases of this size. It lies at 21063'N latitude, 85058'E longitude and 480 m altitude. In the year 2019, there was a total 38.81% forest area of total geographical area. It is bounded by Mayurbhanj district, Balasore district and Bhadrak district to the East, Jajpur district to the South, Dhenkanal district, Anugul district and Sundargarh district to the West, and West Singhbhum district of the state of Jharkhand to the North. The climate of the district is extremely hot in the summers and fairly cold in the winters. Most of its rainfall occurs in the monsoon season. The actual rainfall in the district was 1813.8 mm in the year of 2018-19.
Administratively, the district is divided into 24 sub-districts, 09 towns and 2,123 villages. Oriya is its administrative language. The district came in existence on 1st January, 1948 with the Headquarter in Kendujhar at the distance of 199 kms. from the State Capital.
Demographically, according to the 2011 census, the district has a total number of 4,06,629 households with a total of 18,01,733 comprising 9,06,487 are males, and 8,95,246 are females which leads it to rank 8th in the State and 265th in India. The density of population of the district is 217 (persons per sq kms.). The sex ratio is pegged at 988 (females per 1000 males) while the child ratio stands at 967 (females per 1000 males). As per 2011 census, the percentage of major religions practiced by the people of this region is Hindu with 97.28% of the total population. The population growth rate during the period of 2001-11 was 15.35% including 14.74% are males and 15.97% are females. According to 2011 census the principal language in the district is Oriya with 78.88%. In the year 2017 the number of live births in the district was 29,455 out of which 15,294 were males and 14,161 were females. In the same year the number of deaths in the district was 13,041 out of which 7,374 were males and 5,667 were females.
Economically, the district is dependent on agriculture primarily. The Gross District Domestic Product during 2011-12 was Rs. 20,87,970 lakh at current price and Rs. 7,86,520 lakh at constant prices in the year 2004-2005. The Net District Domestic Product during 2011-12 was Rs. 16,74,382 lakh at current price and Rs. 5,52,252 lakh at constant prices in the year 2004-2005. The Per Capita Income or NDDP, at factor cost during 2011-12 was Rs. 92,211 at current price and Rs. 30,414 at constant prices in the year 2004-2005. It is considered as one of the most backward districts and receiving the Backward Regions Grant Fund. The district has mineral resources such as iron, manganese and chromium ores. There are several small scale industries such as Textile based industries, Power loom industry, Wood and forest industries, Wood and forest industries, bricks manufactures, stone crushing, live stock leather industries and other allied industries.
Education wise, according to the 2011 census, the literacy rate in the district is 68.24% persons including 78.12% are males and 58.28% are females. The total literate population in the district is 10,52,518 comprising 6,05,119 are males and 4,47,399 are females. The district has a number of educational institutes including schools and colleges. Dharanidhar College, Government College of Engineering and Orissa School of Mining Engineering are some of the major institutes in the district.
Ananta Nayak, a veteran member of the Bharatiya Janata Party (BJP). He was the representative of the Keonjhar constituency in the 14th Lok Sabha. He is the present president of the Tribal Morcha.
Many historical and religious tourist places belong to the district are famous worldwide. These places are Ghatagaon, Badaghagara, Sanghagara, Khandadhar, Sitabinj, Gonasika, Murgamahadev, Gundichaghai, Bhimkund. In the year 2018, total 24,86,198 domestic tourists and 198 foreign tourists visited these places of the district. Kendujhar has famous Vishnu Temple, Baladevjew Temple and the shrines of Sidha Jagannath, Siddha Kali and Panchbati amidst picturesque settings. Ghatgaon is famous for the shrine of Goddess Maa Tarini. Sitabinji is located on the bank of the river Sita. Tourists can see the ancient freso paintings on a rock shelter named Ravan Chhaya, looks like a half opened umbrella. Jhadeshwar Temple has an old temple of Lord Shiva. It is located on the bank of River Baitarani. A festival 'Baruni Jatra' is celebrated here. Deogaon (Kushaleswar) is situated on the River Kusei. This place is famous for an image of Abalokiteswar and Buddhist activities in the past time. Murga Mahadev, located on the Thakurani hill in the district is a famous temple dedicated to the Murga Mahadev.