The district derived its name from the Mahendragarh town, which was earlier well known as Kanaud. This previous name of the place was taken from the Kanaudia group of the Brahmins. The region was founded by a servant of Babur named Malik Mahdud Khan. The fort of Mahendragarh was constructed by Maratha ruler called Tantia Tope who ruled the place during the 19th century. Narendra Singh, the ruler of Patiala named the fort as Mahendragarh in honour of his son, Mahendra Singh in the year 1861 and thus the area came to be popularly known as Mahendragarh. Madhogarh Fort, the other nearby fort is located on the top of the hill near Madhogarh village. Mahendragarh was emerged as a separate district in the year 1948 by a collection of different tracts of erstwhile princely states such as Narnaul and Mahendragarh tehsils from Patiala State, Dadri (Charkhi Dadri) from Jind State and a part of Bawal nizamat from Nabha State. After sometime with the merger of Patiala and East Punjab States Union (PEPSU) with Punjab on 1st November 1956, it was automatically included as a part of Punjab state whereas when the Haryana state was formed in 1966, it became a part of it.

Baba Ramdev is a well known personality from the district. He has contributed in Ayurveda, politics and agriculture. He is also a yoga teacher and the founder of the Patanjali Group of Institutions. Sudebar Sujjan Singh was an Indian military officer in the Kumaon Regiment 13th Battalion. He was awarded with the Ashoka Chakra for his bravery.

Geographically, the district has a total 1,899 sq. km. area and occupies the rank 9th in State and 506th in India on the bases of this size. It lies at 28°28'N latitude, 76°15'E longitude and 262 m altitude. In the year 2021, there was a total 5.44% forest area of total geographical area. It is surrounded by Bhiwani and Rewari districts on the North, Rewari and Alwar districts of Rajasthan on the East, Alwar, Jaipur and Sikar districts of Rajasthan on the South and by Sikar and Jhunjhunu districts of Rajasthan on the West. The climate of the district remains extremely hot in summers and fairly cold in winters. The actual rainfall in the district was 745.7 mm in the year of 2021-22.

Administration wise, the district is divided into 2 sub-districts, 5 towns and 370 villages. Hindi is its official language. In the state of Haryana with an allotted district code of 84 the district of Mahendragarh came into existence in the year 1948 with its administrative headquarters located at Narnaul which is situated at a distance of 358 kms from the State Capital.

Demographically, according to the 2011 census, the district is home to a total number of 1,68,525 households with a total of 9,22,088 comprising 4,86,665 are males and 4,35,423 are females and causing it to rank 19th in the State and 463rd in India. The density of population of the district is 486 persons per sq km. The sex ratio is pegged at 895 females per 1000 males while the child ratio stands at 775 females per 1000 males. The schedule caste population of the district is recorded as 1,56,314 including 82,420 are males, and 73,894 are females. The population growth rate during the period 2001 to 2011 was 13.48% out of which 14.89% were males and 11.95% were females. In the year 2020 the number of live births in the district was 13,229 out of which 6,967 were males and 6,261 were females. In the same year the number of deaths in the district was 6,179 out of which 3,717 were males and 2,462 were females. As per 2011 census the major religion n the district is Hindu with 99.04% of the total population. According to 2011 census the principal language in the district is Hindi with 99.53%.

Economically, the district is dependent on the agriculture basically. The GDDP or Gross District Domestic Product during the period 2005-06 was Rs. 2,13,891 lakh at Current Price and Rs. 1,70,666 lakh at Constant Prices during the period 1999-2000. The NDDP, or Net District Domestic Product during the period 2005-06 was Rs. 1,96,302 lakh at Current Price and Rs. 1,56,733 lakh at Constant Prices during the period 1999-2000. The Per Capita Income or NDDP, at factor cost during the period 2011-12 was Rs. 54,835 lakh at Current Price during the period 2004-2005. Mahendergarh is one of the districts which are receiving the Backward Regions Grant Fund Programme (BRGF) from the Government of Harayana.

Education wise, according to the 2011 census, the literacy rate in the district is 77.72% out of which 89.72% are males and 64.57% are females. The total literate population of the district is 6,30,255 including 3,80,440 are males and 2,49,815 are females. The district has a number of educational institutes including schools, colleges and polytechnics. The district has Central University of Haryana. It was established under the The Central Universities Act, 2009". There are several b.ed colleges such as Rohitash College, Ateli Mandi, Saraswati College of Education, Yaduvanshi College of Education, Suraj College of Education, BPS College of Education, etc.

Surjit Singh Barnala is an Indian politician from Shromani Akali Dal. He has served as the Chief Minister of Punjab, former Governor of Tamil Nadu, Uttarakhand, Andhra Pradesh and Andaman and Nicobar Islands and a former Union Minister. Rambilas Sharma belongs to the Bharatiya Janata Party. He is the current Cabinet Minister. He represented the Mahendragarh constituency as a MLA for five times. He was also the former education minister.

The district consists of numerous famous historical and religious tourist places to visit. These places are Jal Mahal, Chor Gumbad, Birbal ka Chhatta, Tomb of Shah Wilayat, Mausoleum of Ibrahim Khan, Nasibpur, Tomb and Tripolia of Shah Quli Khan, Mandir Chamunda Devi, Mandir Chamunda Devi, Dhosi Hill, Bagot, Bamanwas. Jal Mahal is a palace which was built by Nawab Shah Quil Khan, the Governor of Narnaul. It was constructed in 1590-91 A.D. during the Akbar period. The Chor Gumbad is situated upon a rock. Now a park is developed around it. It is well planned and very big in size. It is believed to be constructed during the period of Firoz Shah Tughlaq (1351-88 AD). Bamanvas is a village which is famous for the temple of Baba Rameshwar Dass. The place of Bagot has a very well known Shiva temple. Every year on the occasion of Shiv Ratri a fair is held here. The temple of Chamunda Devi was constructed by Raja Naun Karan. It is situated at the bottom of the hill. A fair is organized here every year on the occasion of Ram Navami. Mughals built a mosque here named Jama Masjid.