Isaac Williams was one of the leading members of the Oxford Movement during the 1830-60s and made a valuable contribution to the movement through his published poetry, tracts, sermons and biblical commentaries which were written to help propagate Tractarian principles. Although he was active in Oxford as a tutor of Trinity College during the 1830s, Williams left Oxford in 1842 after failing to be elected to the university’s chair of poetry. He served successively as perpetual curate of the Gloucestershire parishes of Bisley and Stinchcombe, where he died in 1865. It is perhaps because Williams withdrew from Oxford in 1842 and also because his contribution to the Oxford Movement centred on his literary works rather than on being directly involved in its more practical aspect, that he has tended to be overlooked by historians. This thesis will consider the significance of Isaac Williams’ contribution to the Oxford Movement on the basis of his published works. Whereas previous works on Isaac Williams have examined his significance as a historical figure, this study will focus on his approach to the theological issues with which the Oxford Movement was concerned, specifically, the interpretation of scripture, the sacraments, aspects of High Church/Tractarian piety, the relationship between church and state, the authority of tradition and the apostolic succession. While considering Williams’ approach to these issues, this thesis will also examine whether his theological thinking was at one with that of the Tractarians generally or whether it was more typical of that of the High Church tradition which preceded the Oxford Movement and continued to exist alongside it.