It was an Arab emirate in North Africa that conquered Sicily from Byzantium.
The Aghlabids gained their independence ca. 800 from the Abbasids, during the reign of Harun al-Rashid. Centered in Tunis, the emirate’s powerful fleet was
well positioned to menace Byzantine Sicily, beginning in 826. They achieved effective control over the island with the conquest of Taormina in 902. They captured Malta in 870, and they repeatedly attacked Sardinia as well as cities along the coast of Italy, threatening Rome in 846. Their capture of Bari in 841 allowed them to dominate Apulia for the next three decades until German emperor Louis II reconquered it in 871.
(Source: «Historical Dictionary of Byzantium», by John H. Rosser)