Hisar district is one of the 22 districts of Haryana, India. Hisar city serves as the district headquarters. Hisar district has four sub-divisions that is, Hisar, Barwala, Hansi and Narnaud, each headed by an SDM. The district is also part of Hisar division. Hisar was founded by Firuz Shah Tughlaq.

The largest district in Haryana until its 1966 reorganisation, some parts of Hisar were transferred to the newly created Jind district. In 1974, the Tehsils of Bhiwani and Loharu were transferred to Bhiwani district. Hisar was further bifurcated when Sirsa district was formed. Fatehabad district was later created as well.

Hisar is a divisional headquarters of the Hisar division and also the headquarters of Police Range. It is also a battalion headquarters of B.S.F. 3rd Bn. H.A.P. and commando force. In order to accommodate all of these departments, a five-storey District Administrative Complex was built, with the offices transferred in 1980. It adjoins the new Judiciary Complex, which is also made functional. This administrative and judiciary complex is the largest in Haryana; as a district headquarters it may be one of the largest in the country.

It is one of the five cities belonging to Indus Valley Civilisation while its name is cited in the history books in the context of Indus civilisation and in general knowledge books as the location of Banawali, one of five sheep farms. As of 2011^[update] it is the second most populous of the 21 districts of Haryana, after Faridabad.

Hisar is also known as the steel city because of the Jindal Stainless Steel Factories. It is also the largest producer of galvanised iron in India.^{[citation needed]}

North Hisar district falls in doab between Ghagghar river flowing through fatehabad district and paleo channel of Dhrishadvati river flowing through the Narnaul tehsil. Eastern, central, and south-eastern Hisar district falls in doab between Dhrishadvati river and Yamuna river. Western Hisar district is part of bagar tract. The regions of the doabs near the rivers consist of low-lying, flood-prone, but usually very fertile khadir and the higher-lying land away from the rivers consist of bangar, less prone to flooding but also less fertile on average. For the purpose of irrigation, Hisar district has been classified into 5 circles, namely barani (low rain area where rain-fed dry farming is practised which nowadays are dependent on tubewells for the irrigation), bagar (dry sandy tract of land on the border of Rajasthan state adjoining the states of Haryana and Punjab) nahri (canal-irrigated land), nali or naili (fertile prairie tract between the Ghaggar river and the southern limits of the Saraswati channel depression in northern Hissar district of Haryana that gets flooded during the rains), and Rangoi tract (an area irrigated by the Rangoi canal made for the purpose of carrying flood waters of Ghagghar river to dry areas).

Hisar has fertile alluvial soil interspersed with highly permeable very sandy tracts in bagar region several with water table more than 100 feet below ground containing brackish water usually unfit for human consumption, where dust storms frequent during the warm summer months from April till the end of July when monsoon arrives. Previously, Hisar was solely based on the rain and irrigation was possible only in the nali region where the season Ghaggar river flows in North Hisar. After the opening of Bhakra Nangal Dam canal system in 1963 as well as the earlier Western Yamuna Canal now irrigate most of Haryana including all of the Bagar region falling in Haryana on its western border. Opening of Indira Gandhi Canal in 1983 (specially Hansi Butana branches) brought the water of Sutlej and Beas rivers to the fields of Rajasthan including its Bagar tract stabilising the sand dunes and soil erosion by preventing the expansion of desert.

Hisar has a warm climate.