The siege of Khartoum took place from 13 March 1884 to 26 January 1885. Sudanese Mahdist forces captured the city of Khartoum from its Egyptian garrison, thereby gaining control over the whole of Sudan.

The Mahdist State, also known as Mahdist Sudan or the Sudanese Mahdiyya, was a state based on a religious and political movement launched in 1881 by Muhammad Ahmad bin Abdullah against the Khedivate of Egypt, which had ruled Sudan since 1821. After four years of struggle, the Mahdist rebels overthrew the Ottoman-Egyptian administration and established their own "Islamic and national" government with its capital in Omdurman. Thus, from 1885 the Mahdist government maintained sovereignty and control over the Sudanese territories until its existence was terminated by the Anglo-Egyptian forces in 1898.