The Ansar, or followers of the Mahdi, is a Sufi religious movement in the Sudan whose followers are disciples of Muhammad Ahmad (August 12, 1844 – June 22, 1885), the self-proclaimed Mahdi.

Northern Sudan has long been inhabited by Nubian people who farm the Nile valley and follow a nomadic pastoral way of life elsewhere.

Sudan comes under Egyptian suzerainty when an Ottoman force conquers and occupies the region in 1820–21.

Muhammed Ahmad, a Sudanese religious leader based on Aba Island, proclaims himself Mahdi on June 29, 1881.

His followers win a series of victories against the Egyptians culminating in the capture of Khartoum in January 1885.

Muhammed Ahmad dies a few months later.

His successor, Abdallahi ibn Muhammad, maintains the independence of the Mahdist state until 1898, when an Anglo-Egyptian force regains control.

The Mahdi's eldest surviving son, Abd al-Rahman al-Mahdi, is the religious and political leader of the Ansar throughout most of the colonial era of the Anglo-Egyptian Sudan (1898-1955) and for a few years after the Sudan gains independence in January 1956.

His descendants have led the movement since then.