The Ajuran Sultanate, also spelled as the Ajuuraan Sultanate, and often simply as Ajuran, was a Somali Muslim empire that ruled over large parts of the Horn of Africa in the Middle Ages. Through a strong centralized administration and an aggressive military stance towards invaders, the Ajuran Sultanate successfully resisted an Oromo invasion from the west and a Portuguese incursion from the east during the Gaal Madow and the Ajuran-Portuguese wars. Trading routes dating from the ancient and early medieval periods of Somali maritime enterprise were strengthened or re-established, and foreign trade and commerce in the coastal provinces flourished with ships sailing to and coming from many kingdoms and empires in East Asia, South Asia, Europe, the Near East, North Africa and East Africa.
The empire left an extensive architectural legacy, being the one of the major medieval Somali power engaged in castle and fortress building. Many of the ruined fortifications dotting the landscapes of southern Somalia today are attributed to the Ajuran Sultanate's engineers, including a number of the pillar tomb fields, necropolises and ruined cities built in that era. During the Ajuran period, many regions and people in the southern part of the Horn of Africa converted to Islam because of the theocratic nature of the government. The royal family, the House of Garen, expanded its territories and established its hegemonic rule through a skillful combination of warfare, trade linkages and alliances.
As an hydraulic empire, the Ajuran Empire monopolized the water resources of the Shebelle and Jubba rivers. Through hydraulic engineering, it also constructed many of the limestone wells and cisterns of the state that are still operative and in use today. The rulers developed new systems for agriculture and taxation, which continued to be used in parts of the Horn of Africa as late as the 19th century. The tyrannical rule of the later Ajuran rulers caused multiple rebellions to break out in the empire, and at the end of the 17th century, the Ajuran state disintegrated into several successor kingdoms and states, the most prominent being the Geledi Sultanate.