Due to the importance of water within medieval Islamic civilization brought about by the environmental, religio-cultural, and economical situations in which it evolved, the connection between the patronage of hydraulic structures and the ruling Islamic sovereign played an important role in the creation of medieval Islamic caliphal and kingly identity. This was especially evident throughout the history of the Fatimid rulers of North Africa. For instance, Ibn ‘Idhārī informs us that shortly after defeating the Aghlabids and proclaiming himself the ruler of North Africa, al-Mahdī ordered that the names of all those who had built mosques, cisterns, palaces, and aqueducts be effaced and replaced with his own. al-Mahdī’s actions represent a common notion within medieval Islamic kingship where the ruler was obligated to hold the position of the provider and distributor of water to speak for his legitimacy. Therefore, this paper investigates the connection of water with the notion of legitimacy of the ruler in medieval Islamic culture with particular focus on the Fatimids of North Africa. This study surveys the various Fatimid hydraulic works in the public and palatial arenas in North Africa while investigating the use of an imperial vocabulary in their construction and display to symbolically portray kingly legitimacy and authority. Furthermore, this paper will highlight al-Mu’izz’s construction of an aqueduct directing water from the Cherichera mountains for which he stated that if it could be built from glass he would gladly order that so to complete its construction. al-Mu’izz also compared his efforts for this project to those of Hadrian who built an aqueduct which brought water from the Zaghouan mountains to Carthage which still exists today. Therefore, the paper will also analyze the evolving concept of legitimacy and kingship in Fatimid civilization through the provision of water and through the association of the Islamic sovereign to the past rulers of antiquity and their great architectural works.