Kitaab at-Tawheed' (‘The Book of Monotheism’) is the famous Sunni theologian Abu Mansoor al-Maturidi’s magnum opus (d. 333AH/944AC) and both the work and its author are a foundation of Sunni thought to the present day. Its early provenance and originality, as well as wide and enduring influence, make this book essential for students of theology, philosophy and the history of ideas. Yet despite the wide purported influence of and devotion to his ideas, Maturidi’s work has been strangely neglected and untranslated by Muslim and non-Muslim scholars alike. This is the first ever English translation — with commentary — of the first half of ‘Kitaab at-Tawheed'. This work is unique, providing a detailed and holistic approach to Islamic theology, whilst also being its earliest extant comprehensive source. Maturidi presents the epistemological foundations of his teaching and provides detailed arguments in defence of Monotheism, including his cosmological doctrines — such as proofs for the creation and ontology of the Universe. He also focuses on God, His existence and attributes, analysing issues related to anthropomorphism and rationalism amongst many others. Regardless of theological affiliation, this is an indispensable work for academics and laymen alike.