Sir Sultan Muhammad Shah Aga Khan III (d. 1957), the 48th hereditary Imam of the Shīʿī Ismāʿīlī Muslims, is mostly recognized for his socio-political activities among his Ismāʿīlī flock and the world at large. The late Aga Khan was the President of the All-India Muslim league, the President of the League of Nations, and one of the founders of the republic of Pakistan while also spearheading a number of modernization and social development efforts for his Ismāʿīlī followers. The Aga Khan is among the few Ismāʿīlī Imams to publicly write on theology and metaphysics and his worldview merits careful analysis. Through an exegetical and intertextual analysis of his writings, speeches and Memoirs, this paper argues that the Aga Khan’s theological worldview bears the influence of Fatimid Ismāʿīlī Neoplatonism, the Akbarī doctrine of Waḥdat al-Wujūd, and certain Muslim modernist ideas. The Aga Khan’s metaphysics centres upon the idea of God as the absolute Reality (“Monoreality”) who continuously creates, sustains and manifests the Cosmos through the mediation of an apparently Ismāʿīlī-Neoplatonic hierarchy of hypostases: the Divine Will, the Holy Spirit/Intellect, and the Universal Soul. The Aga Khan’s concept of God, called “monorealism” in contrast to “monotheism”, and his vision of the Cosmos as divine self-manifestation is a rooted in the ontology of Waḥdat al-Wujūd associated with Ibn al-ʿArabī. This Akbarī theo-ontology is also evoked in the memoirs of Aga Khan I, the grandfather of Aga Khan III, and was likely impressed upon Aga Khan III through the influence of his forefathers and his mother. The Aga Khan’s idea of the creative Divine Will, which he describes as a “matrix” or “womb” containing all existence, resembles both Ismāʿīlī and Akbarī notions of God’s Command or All-Merciful Breath. His depiction of the Holy Spirit as the source of spiritual illumination, ultimate happiness and divine inspiration resembles the Ismāʿīlī Neoplatonic idea of the Universal Intellect and he uses similar light imagery to describe the Light (nūr) of Imamat to his followers. His idea of the Universal Soul as the spiritual dimension of the physical Universe, the celestial agency of revelation, and the goal of human souls, is based on a doctrine of Universal Soul from the Fatimid Dā‘ī Nāṣir-i Khusraw. Finally, the Aga Khan’s understanding of the laws of nature as expressions of Divine power and intelligence fuse the classical Ismāʿīlī vision of nature as “incarnate intellect” with certain modernist Muslim conceptions of nature.