This dissertation addresses the ontological significance of poetry in the thought of Martin Heidegger (1889 – 1976). It gives an account of both his earlier and later thinking. The central argument of the dissertation is that poetry, as conceptualised by Heidegger, is beneficial and necessary for the living of an authentic life. The poetry of T. S Eliot (1888 – 1965) features as a sustaining voice throughout the dissertation to validate Heidegger’s ideas and also to demonstrate the uncanny similarity characterising the work of the two men. Chapter one demonstrates how effectively certain concepts from Heidegger’s Being and Time can be applied in an analysis of T.S. Eliot’s celebrated poem The Love Song of J. Alfred Prufrock. The reading involves concepts such as angst, authenticity, inauthenticty, the they and idle talk as they appear in Being and Time and then relates these to aspects of T.S Eliot’s poem. The chapter also enables the reader to perceive the meaning of authenticity and what the authentic life is for Heidegger. Chapter two is an exegesis of Heidegger’s essay The Origin of the Work of Art in order to understand the meaning of poetry as he describes it. The essay centres on the interpretation of a painting by Vincent van Gogh, and what the experience of the painting reveals to someone authentically engaging with the artwork. Heidegger attempts to establish what the essence of a ‘thing’ is (the artwork is a thing), for the origin of the artwork resides in its thingliness. He creates an important distinction between equipment and the artwork as well as earth and the world in order to justify the unique, originary position that the artwork occupies. This leads Heidegger to create a new understanding of poetry (which is expanded to encompass all art forms) and to emphasise the importance of the human agent in both the creation and preservation of the artwork. Chapter three is an exploration of language in both the Heidegger of Being and Time and the later Heidegger’s thought. The aim is to explore the ontological effect that Heidegger’s conception of language has for our existence. He places language within a primordial role in that it is no longer we who speak language, but language that speaks us. This conception has important consequences for our relationship with Being, and the way in which we understand our existence. Another important component of this chapter is the discussion centred on what Heidegger refers to as ‘technological enframing’ (Gestell) and how this adversely restricts the possibilities of language. Language and thought are inextricable phenomena and if their potentiality and possibility are impaired then this will have a detrimental affect on our existence. The final chapter deals with all the themes discussed and serves to unify the various elements of the dissertation into a cohesive argument. The chapter begins with a discussion on the meaning of our existence following the later Heidegger. This is nothing less than the guardianship of Being which can only be understood in its relation to our dwelling within the ‘fourfold’. The terms dwelling, the fourfold, possibility, authenticity (the context of this term has altered somewhat from its initial conception in chapter one) and measure are given special attention, and these terms are unified through Heidegger’s ‘poetic dwelling’ which comes to the fore and serves as the key concept for the chapter. Thus, it is through the measure of the language of poetry that we can realise the possibility of authentic dwelling.