“I deny nothing, but doubt everything,” Byron wrote of his religious views in 1811 (BLJ 2: 136). The complexity of Byron’s religious thought, with its apparent contradictions, its changing nature over time and the deliberate facetiousness with which he often addressed such topics, all make it difficult for commentators to categorize his views. Similarly, the modern loss of sensitivity to questions of theological detail that to Byron were clear and self-evident has meant that many conflicting labels have been applied to Byron’s references to religion in his verse and prose. This chapter considers Byron’s shifting and multiple religious identifications and sympathies, from his engagement with Calvinism to his deism, agnosticism, skepticism and sympathies with Catholicism and Islam, not only in relation to his biography but also within the complex landscape of religious belief and the politics of religion in the Romantic period.