The Funj Sultanate, also known as Funjistan, Sultanate of Sennar (after its capital Sennar) or Blue Sultanate (due to the traditional Sudanese convention of referring to black people as blue) (السلطنة الزرقاء) was a monarchy in what is now Sudan, northwestern Eritrea and western Ethiopia. Founded in 1504 by the Funj people, it quickly converted to Islam, although this embrace was only nominal. Until a more orthodox Islam took hold in the 18th century, the state remained an "African empire with a Muslim façade". It reached its peak in the late 17th century, but declined and eventually fell apart in the 18th and 19th centuries. In 1821, the last sultan, greatly reduced in power, surrendered to the Ottoman Egyptian invasion without a fight.
Christian Nubia, represented by the two medieval kingdoms of Makuria and Alodia, began to decline from the 12th century. By 1365 Makuria had virtually collapsed and was reduced to a petty kingdom restricted to Lower Nubia, until finally disappearing 150 years later. The fate of Alodia is less clear. It has been suggested that it collapsed already as early as the 12th century or shortly after, as archaeology suggests that in this period, Soba ceased to be used as its capital. By the 13th century central Sudan seemed to have disintegrated into various petty states. Between the 14th and 15th centuries Sudan was overran by Bedouin tribes. In the 15th century one of these Bedouins, whom Sudanese traditions refer to as Abdallah Jammah, is recorded to have created a tribal federation and to have subsequently destroyed what was left of Alodia. In the early 16th century Abdallah's federation came under attack of an invader from the south, the Funj.
The ethnic affiliation of the Funj is still disputed. The first and second of the three most prominent theories suggest that they were either Nubians or Shilluk, while, according to the third theory, the Funj were not an ethnic group, but a social class.
In the 14th century a Muslim Funj trader named al-Hajj Faraj al-Funi was involved in the Red Sea trade.