Who was Nizam al-Mulk? In a similar way to ‘Umar II and Charlemagne, Nizam al-Mulk is praised in medieval historiography not just for his political acumen, but also for his knowledge of law, patronage of the clerics, and his ability to stand his ground in religious debate. Nizam al-Mulk crossed the chasm that divided politicians from religious professionals, the one that separated Islamic from Iranian, Sufi from legist, Turk from Persian, Hanafi from Shafi‘i, and sultan from caliph. His uniqueness is reinforced by his enduring legacy, which contrary to current scholarship is shaped not by the Nizamiyya schools, but by his Siyar al-muluk, a guide to good rule written for the Saljuq sultan, Malikshah (r. 1073-1092). This chapter argues that the life of Nizam al-Mulk and its many retellings provide a fulcrum, or an organizing principle, for perceiving the transformation of the social order in medieval Iran.