After Mahdist forces destroyed Khartoum in January 1885, the surviving inhabitants were deported here to the west bank of the White Nile, and the Mahdi's forces began building their new capital around his tomb. Muhammad Ahmad had died of typhus in June 1885, just months after his victory, and his tomb became the spiritual center of Mahdist Sudan. Omdurman grew fast: 150,000 people by some estimates, with wide streets laid out around the tomb and the palace of the Khalifa Abdallahi ibn Muhammad. For thirteen years this was the seat of an independent Sudanese state, with its own flag-workshop (the Tailor of Flags), its own jibba uniforms color-coded by military division, and its own uneasy balance of power between the Mahdi's memory and the Khalifa's authority.

On September 2, 1898, British-led forces under Herbert Kitchener reached the village of Kerreri, just north of Omdurman, with 20,000 men, Maxim guns, and Martini-Henry rifles. The Mahdist army that came out to meet them numbered 52,000, many of them Sudanese villagers armed with swords, spears, and rifles captured from earlier battles. The engagement lasted five hours. The machine guns did the work. At least 10,000 Mahdists died, most without getting close enough to return fire. Kitchener lost 48 men. Then Kitchener marched into Omdurman and ordered the Mahdi's tomb desecrated. Winston Churchill, who was there as a young cavalry officer, wrote that Kitchener carried off the Mahdi's skull in a kerosene can as a trophy. It was an act that shocked even some British officers. The tomb would be restored decades later. The skull, eventually, was buried in a Muslim grave at Wadi Halfa.

Kitchener moved the capital back across the Nile to Khartoum and rebuilt it on a street plan shaped like the Union Jack. But Omdurman did not empty out. The Mahdi's tomb was refurbished and became, and remains, a major Islamic pilgrimage site. The old dervish traditions, the Friday gatherings where Sufi drummers and chanters reach ecstatic states, have continued without interruption for more than a century. Hamad al-Nil mosque in the Umbadda district fills every Friday afternoon with green-robed Sufi dancers whirling until the sun sets. The Khalifa's House, the former palace, became a museum. The market, Souq Omdurman, remains the best place in Sudan for silver jewelry, Nubian leatherwork, and sandalwood.

Omdurman sits where the White Nile's west bank turns. Khartoum is directly across the river, joined by bridges; Khartoum Bahri is upstream to the east. The climate is ferocious. Six months of the year the average monthly high exceeds 38°C. No month's average high drops below 30°C. In summer, temperatures routinely pass 40°C, and the rains, when they come, total only about 155 millimeters per year. The January-February nights cool off enough for a light jacket. Everything else is variations on heat. The city's universities, including the Omdurman Islamic University and Ahfad University for Women (a remarkable institution founded in 1966 specifically to educate Sudanese women), draw students from across the country. The football clubs, Al Merreikh and Al Hilal, divide Omdurman more bitterly than any political dispute ever has.

From April 2023 to May 2025, the Rapid Support Forces occupied Omdurman during the Sudanese civil war. The Mahdi's tomb, the museums, the universities, the football stadiums, the Friday gathering at Hamad al-Nil, all suspended, all under threat. Residents fled in vast numbers or hid in neighborhoods that the fighting had not yet reached. The Sudanese Armed Forces retook the city in May 2025, and the reconstruction began. The people of Omdurman have seen their city destroyed and rebuilt before. Mahdists, British, coup governments, RSF. Each generation has thought its turn was the worst. Each has watched the next generation rebuild. The mother in the city's name may be forgotten, but her children persist.