Abstract: The Abbasid Golden Age represents one of the most remarkable periods of scientific and philosophical advancement in human history, characterized by the massive Greco-Arabic translation movement, the establishment of institutions like the Bait al-Ḥikma (House of Wisdom) in Baghdad, and original contributions in fields such as mathematics, astronomy, medicine, optics, and philosophy. During this period the rationalist theology of the Mutazila school played a pivotal catalytic role in fostering this era’s intellectual dynamism. Emerging in the early 8th century in Basra and founded by figures like Wasil ibn Ata, the Mutazila emphasized human reason (aql) as a tool for understanding divine truths, divine justice (adl), free will, and the created nature of the Quran. This rationalist framework created an intellectual environment conducive to empirical inquiry and natural causality, countering occasionalist views that later dominated under Asharite theology. Under Caliph al-Mamun, a staunch patron of learning and Mutazilite doctrine, the school reached its zenith. Al-Mamun's support for rationalism aligned with state-sponsored translation efforts, bringing Greek, Syriac, Persian, and Indian scientific texts into Arabic. It highlights the Mutazila's enduring legacy in reconciling revelation with rational inquiry, offering insights for contemporary science-religion dialogues in Islamic contexts. Keywords: Mutazila, Rationalism, Golden Age, Abbasids.