This study examines the functions of religion in Shihāb al-Dīn Suhrawardī’s thought and its place within Illuminationist philosophy, focusing on knowledge, spiritual purification, social life, and humanity’s ultimate purpose. Using a descriptive-analytical approach, it draws on Suhrawardī’s writings and scholarship on Illuminationist philosophy. The findings identify four principal functions of religion: an epistemic function, whereby revelation and religious law refine the intellect and prepare the soul for intuitive apprehension of luminous realities; an educational-ethical function, realized through spiritual purification, spiritual striving, and adherence to religious law; a sociopolitical function, fulfilled through the guidance and organization of society by the prophet and the divinely realized sage; and an existential-teleological function, explaining humanity’s journey from darkness to light and attainment of eternal felicity. The study concludes that religion is foundational to Illuminationist accounts of knowledge, moral perfection, social order, and humanity’s ultimate end. The integration of religious law, reason, and intuitive insight provides a coherent framework for attaining human perfection.