The work examines the presence and significance of Kierkegaard in Heidegger's work. After setting out the context of Heidegger's reception of the Danish thinker and examining his likely knowledge of his writings, the work first examines key Kierkegaardian concepts that are explicitly present in Being and Time, including existence, 'idle talk' (Gerede), anxiety, the moment of vision, repetition, and the existential significance of death. It is seen that Heidegger regarded Kierkegaard as an essentially religious writer whose work was only indirectly relevant to Heidegger's own project of fundamental ontology. Subsequently, the work considers the place of Kierkegaard in Heidegger's writings from the 1930s onwards, concluding with consideration of the paper Heidegger submitted for the 1963 Paris UNESCO conference marking the 150th anniversary of Kierkegaard's thought.