Ulugh Beg b. Shahrukh (r. 1409-47), Timurid ruler of Transoxania, is justly famed as founder of the Samarkand Observatory and Madrasa, the most important scientific complex of the 15th-century Islamo-Christianate world. Not only did he assemble a team of mathematical astronomers who would revolutionize the science, but performed the role of competent scientist himself—hence Qazizada Rumi’s (fl. 1440) striking title for his patron: al-sultan al-faylasuf, the sultan-scientist. Most notably, Ulugh Beg’s scientific team was responsible for mathematizing the cosmos, this through their unprecedented divorce of aristotelian physics from astronomy. This fateful project has been well feted in current scholarship as the immediate intellectual precedent for Copernicus, Kepler and Newton; but its broader neopythagorean-occultist context has been wholly elided, which in turn has obscured Ulugh Beg’s status as claimant to a peculiarly Timurid form of (occult) philosopher-kingship. The model here is Ulugh Beg’s cousin and would-be successor to Temür, Iskandar Sultan (r. 1409-14), whose patronage of the occult sciences, especially lettrism and astrology, was far more explicit. Nevertheless, the surviving textual record suggests that Ulugh Beg was equally familiar with the occult-scientific works with which Iskandar Sultan fashioned and performed his Timurid sovereignty. This paper restores Ulugh Beg’s title of sultan-scientist to its original neopythagorean-occultist context with reference to three such works. Specifically, it cannot be considered coincidental that construction of the Samarkand Observatory was begun the same year, 1420, that Ibn Turka (d. 1432) completed his landmark Book of Inquiries (K. al-Mafahis)—the first summa of Islamic neopythagoreanism, which opens precisely with a call for a mathematical revolution. The same lettrist thinker—whose first patron was precisely Iskandar Sultan, and a close friend and colleague to Qazizada Rumi—further dedicated his Sharh al-Basmala (1426) to Ulugh Beg. Equally suggestive is the fact, moreover, that ‘Abd al-Qadir Ruyani Lahiji (d. 1519), ‘Ali Qushchi’s (d. 1474) protégé, produced the Key of Keys (Miftah-i Mafatih), one of the Persianate world’s most popular manuals of geomancy. It was thus in recognition of Ulugh Beg’s accession to occult philosopher-kingship that Ibn Turka exclaims in his dedication to the Timurid sultan-scientist: “Long have I held out hope for just such a time—and that time is yours!”