Deoria district is one of the districts of Uttar Pradesh state of India, and Deoria town is the district headquarters. Deoria district is a part of Gorakhpur division.

The area now known as the Deoria District was once a part of the Kosala Kingdom – a prime centre of ancient Aryan culture surrounded by the Himalayas in the north, the Shyandika river in the south, the Panchala Kingdom in the west and the Magadh Kingdom in Bihar to the east. Apart from the many legends told about this area, archaeological remains, such as statues, coins, bricks, temples, and Budh Maths, have been discovered at many locations in this district, showing that there was a developed and organised society long ago.

Ancient history of the district is related with the Ramayana times when the Lord of Kosala, Ram, appointed his elder son Kusha the king of Kushwati, which is present-day Kushinagar. Before the Mahabharata era, this area had been related with Chakravorty Samrat Mahasudtsan Mall and his kingdom. Kushinagar was well developed and prosperous. Close to the border of his kingdom was the thick forested area called the Mahavan. This area was under the control of the Maurya rulers, the Gupta rulers, the Bihar rulers, and then the Garhwal ruler Govinda Chandra from 1114 AD until 1154 AD.

The Deoria district came into existence on March 16, 1946, being separated from the Gorakhpur District. It is believed that the name Deoria is derived from Devaranya or possibly Devpuria. According to official gazetteers, the district was named “Deoria” after its headquarters in Deoria, and the term Deoria generally means a place where there are temples. The name Deoria probably developed because of the existence of important temples in the area. During Freedom struggle of India the district joined struggle under the leadership of Pandit Bibhuti Mani Tripathi of village Dehrauli, Rudrapur. He provided leadership and invited Subhash Chandra Bose in district to inspire youths.

Deoria district is located between 26 ° 6′ and 27° 8′ north latitude to 83° 29′ and 84° 26′ east longitude. It is surrounded by Kushinagar district in the north, Gopalganj and Siwan districts of Bihar in the east, Mau and Ballia districts in the south and Gorakhpur district in the west.

According to the 2011 census Deoria district has a population of 3,098,637, roughly equal to the nation of Mongolia or the US state of Iowa.This gives it a ranking of 114th in India (out of a total of 640).The district has a population density of 1,220 inhabitants per square kilometre (3,200/sq mi).Its population growth rate over the decade 2001-2011 was 14.23%.Deoria has a sex ratio of 1013 females for every 1000 males, and a literacy rate of 73.53%.

Vernaculars spoken in Deoria include Bhojpuri, a language in the Bihari languages group and Hindi with English language English almost 40 000 speakers, written in both the Devanagari and Kaithi.