Omdurman (standard Arabic Umm Durmān أم درمان) is the largest city in Sudan and Khartoum State, lying on the western banks of the River Nile, opposite the capital, Khartoum. Omdurman has a population of 2,395,159 (2008) and is the national centre of commerce. With Khartoum and Khartoum North or Bahri, it forms the cultural and industrial heart of the nation.

In 1884, Muḥammad Aḥmad, "the Mahdi", made his military headquarters in the village of Omdurman. The conflicts that followed over the next fifteen years have become known as the Mahdist War. Following the defeat of the besieged defenders of Khartoum in 1885, the Mahdi's successor, Khalifa ʻAbdullahi ibn Muḥammad, made Omdurman his capital.

The city, now the location of the tomb of the Mahdi, grew rapidly. However, in the Battle of Omdurman in 1898 (which actually took place in the nearby village of Kerreri), Lord Kitchener decisively defeated the Mahdist forces, ensuring British control over the Sudan, and killed Khalifa.

Kitchener restored Khartoum as the capital and, from 1899 until 1956 Sudan was jointly governed by Great Britain and Egypt. Although most of the city was destroyed in the battle, the Mahdi's tomb was restored and refurbished.