This paper aims at approaching the topic of mortality in Kierkegaard with special regard to the figure of the Wandering Jew. The legendary character of Ahasverus is detectable across the lines of the Unhappiest one (Enten Eller, I 1843) and at the background of Sickness unto death (1849) in addition to a series of scattered references. According to the folkloric tale, accessed by Kierkegaard mainly via Ludwig Aurbacher's Ein Volksbüchlein (1835), Ahasverus prevented Jesus to have a rest during his rise to the Cross. Therefore, he was cursed and condemned not to be able to die. Kierkegaard's understanding of the Wandering Jew casts light on his concept of despair (Fortvivelse) as «sickness unto death», that is eternally living the death of the spirit, which by its definition cannot die. Starting from Kierkegaard's meditation on the Jerusalem Shoemaker, the paper will end up by distinguishing three different nuances of mortality into Kierkegaard's thought: natural death as finitude, spiritual death as despair, and Christian death as fulfilment. Since natural death is a "non-possibility" for human beings, these latter are called in the end to choice between despair and faith.