Siwan district is situated in the western part of Bihar. Siwan got its name from "Shiva Man", a Bandh Raja whose heirs ruled the area till Babar’s arrival. The term "Siwan" means boarder in Bhojpuri language, earlier the district used to be the boarder district of Bihar. Originally, Siwan was a sub-division of Saran District. Siwan as a separate state came into existence in 1972 when it was split from Saran district.

Siwan district, situated in the western part of the state, was originally a sub-division of Saran district, which in ancient time formed a part of Kosala Kingdom. Siwan became a fully-fledged district when it was split from Saran in 1976. Siwan derived its name from "Shiva Man", a Bandh Raja whose heirs ruled this area till Babar’s arrival. The meaning of "Siwan" is border, previously it used to be the border district of "Bihar". Maharajganj, which is another subdivision of Siwan district, may have found its name from the seat of the Maharaja there. A recently excavated marvelous statue of Lord Vishnu at Bherbania village from underneath a tree indicates that there were large numbers of followers of Lord Vishnu. It is now dominated by Yadavs and Rajputs.

Mulana Mazharul Haque, a well-known politician, who helped to organize the Home Rule Movement in Bihar, was born in 1866 at Bahpura (Simli), Bihar. In 1916 he was the President of Home Rule Movement in Bihar. Satyendra Dubey, a brave Indian Engineering Service (IES) officer was born on 27th November, 1973 at the Sahpur village in the Siwan district. He was the Project Director in the National Highways Authority of India (NHAI) at Koderma.

Geographically, the district lies at 26°22'N latitude, 84°36'E longitude and 77 m Altitude. In the year 2021, there was a total 0.35% forest area of total geographical area. The district encompasses with a total area of 2,219 sq kms. and it is bordered by Saran district on the east, Gopalganj on the north, Deoria on the west and Ballia on the south. Ghaghara River is the prime river of the district. The climate of the district is hot and drier. In the month of May and June the natives of the district experiences 'Loo'. During the winter season the climate of the district remains pleasant with low temperature. Most of its rainfall occurs in the monsoon season. The actual rainfall in the district was 1663.1 mm in the year of 2021-22.

Administrative wise, the district comprises of 2 sub divisions-Siwan and Maharajganj. To administer in a better way the district is divided into 19 functional blocks. Siwan is the only Lok Sabha Constituencies of the district. Moreover, the district consists of 8 Assembly seats. The district also comprises 3 towns and 1530 villages. The administrative language in the district is Hindi.

According to 2011 census the district has a population of 33,30,464 out of which 16,75,090 are males and 16,55,374 are females. The district has a sex ratio of 988 females for every 1000 males. During the year 2001-2011 the population growth rate of the district was 22.70% including 25.35% were males and 20.12% were females. As per 2011 census the major religions in the district are Hindu and Muslim with 81.45% and 18.26% of the total population. The population density in the district is 1,501 persons per sq. km. According to 2011 census the principal language in the district is Hindi with 95.56%. In the year 2020 the number of live births in the district was 92,041 out of which 49,156 were males and 42,874 were females. In the same year the number of deaths in the district was 15,644 out of which 9,610 were males and 6,034 were females.

The economy of Siwan district is mainly based on agriculture. The core agricultural crops of the district are wheat, rice, maize, sugarcane and potatoes. The district of Siwan possesses a good amount of potential for artisan based industry in comparison to other districts of Bihar. Moreover, the dairy sector of the district also contributes in its economy. In the year 2011-12 the gross domestic product of the district was Rs. 5,71,012 lakhs at current price and Rs. 3,34,235 at constant prices in the year 2004-05. In the year 2011-12 the net domestic product in the district was Rs. 5,18,515 lakh at current price and Rs. 2,99,391 lakh at constant prices in the year 2004-05.

Siwan is not a great platform for higher education. According to 2011 census the literacy rate of the district is 69.45% including 80.23% are males and 58.66% are females. The number of literates in the district is 19,30,175 out of which 11,15,906 are males and 8,14,269 are females.

Dr. Rajendra Prasad, a veteran politician and the first President of the Republic of India was born on 3rd December, 1884 at Ziradei in Siwan. He joined the Indian National Congress during the Indian independence movement and became a major leader from Bihar. He was also honoured by Bharat Ratna Award. Mahamaya Prasad Sinha, an eminent Indian politician and the Chief Minister of Bihar from March, 1967 to January, 1968 was born on 1st May, 1909 in Siwan. He was elected to the 6th Lok Sabha from the Patna constituency of  Bihar in 1977.

Every year numerous travellers come to this district to enjoy its historical places and ancient temples. Zeeradei is situated about 13 km. from the district head quarters and it is the birthplace of India's first president Dr. Rajendra Prasad. Ashiana is a place which is known as the native residence of Maulana Mazharul Haque, one of the greatest freedom fighters and a symbol of Hindu-Muslim unity of the country. Anand Bagh Math and Sunder Bagh Math are situated at Bakhri village in Siswan block of Siwanthe. These two temples are built on the "samadhi sthals" of two renowned saints, Swami Jaggannath Das ji and his guru Bhagwan das ji. Mahendra Nath Temple, a temple of Lord Shiva is situated in Mehdar village under Siswan block of the district. Raghunathpur is a place situated about 27 kms. south from the district head quarters. Natives believe that Lord Rama had taken rest in the place after killing demon Tarka near Buxar. Panchmukhi Shivalinga or five faced Shivalinga of an old Shiva temple in Mahadeva locality of Siwan town attracts a huge number of tourists from far distance place. Burhiya Mai Temple allures huge crowd of pilgrims, especially on Saturdays. The temple is situated on east-northern portion of Gandhi Maidan in Siwan town. Amarpur, Faridpur, Darauli and Don are some of the not able historical places of the district.