The Funj Sultanate of Sennar (sometimes spelled Sinnar), known in Sudanese traditions as the Blue Sultanate (Arabic: السلطنة الزرقاء; As-Saltana az-Zarqa‎), was a sultanate in the north of Sudan, named Funj after the ethnic group of its dynasty or Sinnar (or Sennar) after its capital, which ruled a substantial area of northeast Africa between 1504 and 1821.

In the 15th century the part of Nubia formerly controlled by Makuria was home to a number of small states and subject to frequent incursions by desert nomads. The situation in Alodia is less well known, but it also seems as though that state had collapsed. The area was reunified under Abdallah Jamma, the gatherer, who came from the eastern regions that had grown wealthy and powerful from the trade on the Red Sea. Abdallah's empire was short lived as in the early 16th century the Funj people under Amara Dunqas arrived from the south, having been driven north by the Shilluk. The Funj defeated Abdallah and set up their own kingdom based at Sennar.

Sennar (Arabic: سنار‎ Sannār) is a town on the Blue Nile in Sudan and capital of the state of Sennar. For several centuries it was the capital of the Funj Kingdom of Sennar. It had an estimated population of 100,000 inhabitants in the early 19th century. The modern town lies 17 km SSE of the ruins of the ancient capital. It is located close to Sennar Dam, which spurred agricultural activity when it was created in 1925 for crop irrigation. The Sinnar Dam was designed, built and subsequently managed by the English engineer, Stephen "Roy" Sherlock.

Today there are two towns bearing the name Sennar. Sennar Junction, the older one, which represents an actual continuation to the ancient Sennar, both in time and geographical location, the junction element came from the fact that many railways intersect there, it being in the heart of the country, which accompanied the invasion of Sudan during the British colonisation at the end of eighteenth century. The other is Sennar Al-Madeena (i.e. Sennar Town), 5 km ESE of the Junction, located beside the Sennar Dam. It was built over the ruins of a small village called Mok-waar which was notable in the former cultures of the tribes of African origins who lived there before the arrival of Arab tribes to the Sudan.