Abdullah Ibn-Mohammed or Abdullah al-Taashi or Abdullah al-Taaisha, also known as "The Khalifa" (Arabic: c. عبدالله بن سيد محمد خليفة‎; 1846 – November 25, 1899) was a Sudanese Ansar ruler (like king or royal) who was one of the principal followers of Muhammad Ahmad. Ahmad claimed to be the Mahdi, building up a large following. After his death Abdallahi ibn Muhammad took over the movement, adopting the title of Khalifat al-Mahdi (usually rendered as "Khalifa").