The district is named after its Headquarter town, Unnao. About 1200 years ago, the site of this town was covered with extensive forests. Godo Singh, a Chauhan Rajput, cleared the forests probably in the the 3rd quarter of the 12th Century and founded a town, called Sawai Godo, which shortly afterwards passed into the hands of the rulers of the Kannauj, who appointed Khande Singh as the Governor of the place. Unwant Singh, a Bisen Rajput and a lieutenant of the Governor, killed him and built a fort here, renaming the place as Unnao after himself..

District Unnao Situated between the cities of Lucknow & Kanpur, Unnao has a rich heritage of sword and pen, having produced great freedom fighters, poets and writers. The freedom struggle of 1857-1858 was followed by the transfer of power from the East India Company to the British Crown. As soon as order had been restored, the civil administration was re-established in the district which was named district Unnao, with headquarters at Unnao.

The size of the district was however small till 1869, when it assumed its present form. The same year the town of Unnao was constituted a Municipality.Hiuen Tsang, the famous chinese pilgrim to India, stayed at Kannauj for 3 months in 636 AD. From here he journeyed adistance of about 26 kms and reached the city of Na-fo-ti-po-ku-lo (Navadevakula) which stood on the eastern bank of Ganga. The city was about 5 km in circumference and had in or about it, a magnificent Deva Temple, several Buddhist Monasteries and Stupas.