This district was carved out on 17 May 1983 by separating Rajmahal and Pakur sub-divisions of erstwhile Santhal Parganas district. Pakur sub-division was again separated on 28 January 1994 to form Pakur district.
The territory of the present district was a part of Bengal Subah of the Mughal empire. Rajmahal, a place located in the district was made the capital of Bengal Subah in 1592 by Raja Man Singh, a general of the Mughal Emperor Akbar for the first time. It again became the capital of Bengal Subah in 1639, when Shah Shuja was appointed the Subahdar and it remained so till 1660.
The district lies approximately between 24°42’ and 25°20’ north latitudes and between 87°25’ and 87°54’ east longitudes. This district covers an area of 1599 km².
The district can be divided into two natural divisions based on its geographical features. The first region consists Borio, Mandro, Barhait, Pathna and Taljhari blocks and it is a part of the Damin-i-koh region. The hills and its slopes are covered with forests, once dense but scanty now. The second region consists Sahibganj, Rajmahal, Udhwa and Barharwa blocks. This plain region comprises the uplands, undulation along ridges and depressions. The Ganges, Gumani and Bansloi rivers flow through this region.
The district comprises two sub-divisions: Sahibganj and Rajmahal. Sahibganj sub-division consists 4 blocks: Sahibganj, Mandro, Borio and Barhait. Rajmahal sub-division consists five blocks: Taljhari, Rajmahal, Udhwa, Pathna and Barharwa.
There are three Vidhan Sabha constituencies in this district: Rajmahal, Borio and Barhait. All three are part of Rajmahal Lok Sabha constituency.
Udhwa Bird Sanctuary, the only bird sanctuary of Jharkhand state is located in the district, near a place called Udhwa, which is locally called Patauda Lake. Migratory birds reach here every winter from several parts of the World, including Siberia.