Ahmadu Seku (died 1898, Sokoto, Northern Nigeria) was the second and last ruler of the Tukulor empire in West Africa, celebrated for his resistance to the French occupation.
Succeeding his father, al-Ḥājj ʿUmar, in 1864, Ahmadu ruled over a great empire centred on the ancient Bambara kingdom of Segu, in present Mali. By the Treaty of Nango (1881) he granted France most-favoured-nation status. After the advance of the French to Kita and Bamako, he abandoned Segu as his capital and accepted a French protectorate (Treaty of Gouri, May 12, 1887). But Col. Louis Archinard took the offensive against him in 1888 and by 1891 had seized most of his strongholds.