“Que Voulez-Vous?” : what do you expect? (Waiting for Godot 56) “What is it I'm looking for? I know it's something I lost.” (Long Day’s Journey into Night 107) These similar questions are addressed by Samuel Beckett and Eugene O‟Neill in their dramas. Interestingly, Beckett‟s “Que Voulez-Vous?” and O‟Neill‟s “What am I looking for?” resonate with Christ‟s question to his two followers: “What do you want?” (John1:38) This simple but crucial question strikes at the heart of humanity, hankering for something that they have lost and not yet found; this something may be God. Modernist theatre relies on the Nietzschean concept of „the death of God‟. This point is seen to relate to the work of Eugene O'Neill and Samuel Beckett. Both O'Neill and Beckett were brought up in pious Irish families. Nonetheless, their reaction to their Irish roots was mixed with blasphemy, and nostalgia for the loss of their Christian heritage. My thesis in this respect addresses the following question: how do O'Neill and Beckett represent on stage their spiritual frustration and longing for God? To examine this question, I explore representative drama by O‟Neill and Beckett, focusing upon tragedy, nihilistic philosophy, and Christianity. Drawing on these sources, this thesis aims to analyse a theatrical aesthetic that, despite initial appearances, exhibits a strong metaphysical and theological dimension. This thesis is divided into two main parts. In the first part, I examine O'Neill's Beyond the Horizon, The Fountain, Lazarus Laughed, The Hairy Ape, Dynamo, and Long Day’s Journey Into Night. In the second part, I focus on Beckett's Waiting for Godot. The conclusion reads these two distinct playwrights in conjunction by formulating comparative observation. In this regard, I try to connect their work with different perspectives, taking account of literary, philosophical and theological approaches. This interdisciplinary reading can neither completely eliminate repetitions nor overcome the fragmentary nature of each approach. Nevertheless, I hope to gain a deeper understanding of the ways in which the works of O'Neill and Beckett conceive of Christianity in both its positive and negative characterization.