Jhajjar district is one of the 21 districts of Haryana state in northern India. Carved out of Rohtak district on 15 July 1997 and with its headquarters in Jhajjar, it lies 29 kilometres (18 mi) from Delhi and had developed into an important industrial center. Other towns in the district are Bahadurgarh and Beri.

The district occupies an area of 1,834 square kilometres (708 sq mi) and as of 2001 its population was 709,000. It has two industrial areas with 2408 plots. Basic industries are ceramics, glass, chemicals, engineering, electrical and electronics. There are 48 large and medium units along with 213 small scale units representing a total investment of Rs. 3400 million ($76.5 million) and a workforce of 8,248. Major crops grown here are rice, wheat and maize. The total irrigated agricultural land area is about 670 square kilometres (260 sq mi).

Jhajjar is said to have been founded by Chhaju as Chhajunagar, which was later changed to Jhajjar. Alternatively, it may be derived from Jharnaghar, meaning a natural fountain or Jhajjar, a water vessel, because the surface drainage of the country for miles around runs into the town as into a sink. Bahadurgarh, founded by Rathi Jats, was formerly known as Sharafabad.

As of the 2011 census Jhajjar district had a population of 956,907, roughly equal to the nation of Fiji or the US state of Montana.This gives it a ranking of 456th in India (out of a total of 640).The district has a population density of 522 inhabitants per square kilometre (1,350/sq mi).Its population growth rate over the decade 2001-2011 was 8.73%.Jhajjar has a sex ratio of 782 females for every 1000 males, and a literacy rate of 80.8%.Jat is the dominant caste in the district with sizable Brahmin population, while Ahirs hold one village.