Abdullah Ibn-Mohammed Al-Khalifa or Abdullah al-Khalifa or Abdullahi al-Khalifa, also known as "The Khalifa" (1846 – November 25, 1899) is a Sudanese Ansar ruler who is one of the principal followers of Muhammad Ahmad.

Ahmad claims to be the Mahdi, building up a large following.

After his death Abdulah ibn Muhammad takes over the movement, adopting the title of Khalifat al-Mahdi (usually rendered as "Khalifa").

He attempts to create a kingdom, which leads to widespread discontent, and his eventual defeat and death at the hands of the British.