Sudan , officially the Republic of the Sudan , is a country in Northeast Africa. It is bordered by Egypt to the north, Libya to the northwest, Chad to the west, the Central African Republic to the southwest, South Sudan to the south, Ethiopia to the southeast, Eritrea to the east, and the Red Sea to the northeast. Sudan has a population of 44.91 million people as of 2021 and occupies 1,886,068 square kilometres (728,215 square miles), making it Africa's third-largest country by area and also the third-largest by area in the Arab league. It was also the largest country by area in Africa and the Arab league by area before the secession of South Sudan in 2011, since which both titles have been held by Algeria. Sudan's history goes back to the Pharaonic period, witnessing the Kingdom of Kerma (c. 2500–1500 BC), the subsequent rule of the Egyptian New Kingdom (c. 1500 BC–1070 BC) and the rise of the Kingdom of Kush (c. 785 BC–350 AD), which would in turn control Egypt itself for nearly a century. After the fall of Kush, the Nubians formed the three Christian kingdoms of Nobatia, Makuria and Alodia, with the latter two lasting until around 1500. Between the 14th and 15th centuries, much of Sudan was settled by Arab nomads. From the 16th–19th centuries, central and eastern Sudan were dominated by the Funj sultanate, while Darfur ruled the west and the Ottomans the far north. From the 19th century, the entirety of Sudan was conquered by Egypt under the Muhammad Ali dynasty. It was under Egyptian rule that Sudan acquired its modern borders, and began the process of political, agricultural, and economic development. In 1881, nationalist sentiment in Egypt led to the Orabi Revolt, weakening the power of the Egyptian monarchy, and eventually leading to the occupation of Egypt by the United Kingdom.