This study explores the impact of religion on Byron's poetry. It will not only examine the effects of his Calvinist upbringing but also investigate how this influenced his attraction to and utilisation of Dualist heresies in his poetry. The first Chapter looks at the reasons behind Byron's repudiation of his Scottish Calvinist heritage caused by his negative perceptions of its God and its adherents. This will be followed by an exploration of the effects that this Calvinism had on Byron's mental state, with particular reference to the uniquely Calvinist form of depression known as Religious Despair. The second Chapter will argue that it was his rejection of Calvinist doctrines and abhorrence of the Calvinist God that caused Byron to search for alternative answers to the existence of evil, eventually leading him to Dualism in its various forms. After an examination of the numerous sources of information on Dualism that Byron encountered, both historical and doctrinal, there will be a detailed analysis of the presence of Dualism in his poetry. The third Chapter considers the purpose behind Byron's adaptation of Dualist imagery and ideology and its presence in his poetry. This will be achieved by first addressing the ways he uses Dualist doctrines and imagery to subvert Calvinist teachings and precepts, and then by detailing the surprisingly numerous parallels between Calvinism and Dualism. Particular attention will be paid to Byron's use of light and dark, linking it back to his remarkably complex relationship with the various religions that influenced him. An awareness of Byron's interest in these religions can serve to provide a new and useful reading of his texts. Although there have been various works briefly touching upon the influence of different religions and philosophies on Byron's poetry, there has been no serious consideration of the overall effect and consequences of Byron's interaction with these faiths. Nor has there been a full, detailed examination of the sources of his knowledge, his understanding of them and the use which he makes of this knowledge in his writings. I say writings, as this thesis will rely on his letters and journals as evidentiary sources with a value almost equal to that of his poetry. In this context, the thesis considers Byron's letters and journals as evidentiary sources alongside his poetry and plays. Moreover, the persistence in Byron's career and subsequent reception of a conflation between poet and poetry, creator and creation, by Byron's friends, family and critics means that his reputation and perception by his peers must also be considered and analysed as part of his artistic endeavour, particularly given his grasp of 'spin' and cult of publicity. Finally, in challenging Calvinism and its adherents through a variety of means, including the appropriation of Dualist imagery and theology, Byron operated within a tradition that had an established history. The presence of several religious ideologies in his poetry will be contextualised by contrasting Byron's poetry with other literary works which present these faiths in a similar fashion.