A practice predicated upon the verbatim re-presentation of non-fiction documents, interviews, personal writings, and other historical source materials on stage, documentary theatre frequently claims to produce theatrical experiences that represent ‘reality’ and ‘truth’. Yet, the symbiosis of real-world source material and a dynamic dramaturgy can be an intricate balancing act, as the theatre maker is often faced with the challenge of how to best navigate the tension between accurately representing ‘the real’ on stage and producing a dynamic theatre experience. Much of the scholarship engaging with documentary theatre has addressed the complex ethical-political process of speaking for others and the risk of misrepresentation that comes with making a real person into a documentary character. Consequently, theatre makers often strive to not only represent their documentary subjects accurately but also aim to increase their agency in the documentary theatre process by facilitating opportunities for dialogue, connection, and collaboration. Yet what happens when the theatre maker is unable to communicate with their subjects or extend a collaborative hand? Posthumous Documentary Theatre: Re-presenting Historical Documentary Material on Stage addresses a gap in the documentary theatre discourse and explores how the potential ethical considerations associated with the form may be further complicated when the documentary subjects are no longer living. This research takes the form of a PhD with a creative practice component that involved the creation of What Remains: The Love and Letters of Vita Sackville-West & Harold Nicolson. An original documentary play constructed primarily from posthumously published letters and personal writings; What Remains enabled a practical exploration of how theatre makers' ethical considerations for their deceased documentary subjects might influence their dramaturgical processes. Synthesising critical reflection on that creative process with existing documentary theatre theories and practices, this thesis offers findings that aim to be practically useful to others navigating the intersecting ethical and dramaturgical demands of representing the dead on stage in documentary theatre.