Adaptation is an ever-expanding field of study, with new trends and terms established in response to the proliferation of media. This thesis investigates how theatrical adaptation fits into emerging adaptation discourses, particularly the idea of transmediality. Although theatre is often side-lined in adaptation studies, this thesis argues that theatrical adaptation embodies various historical and contemporary adaptation trends. This thesis also contends that, in line with current understandings of media specific qualities, and media theory, adapting from any form of media to the stage is inherently transmedial. Investigating contemporary theatrical adaptation adapted from differing forms of media (novel, picturebook, comic), this thesis will highlight the processes of adaptation, in both creation, and reception. Focusing on the narrative in three adaptive stages – the original text, the script adaptation, and then the productions of that script – this thesis will highlight the key adaptation concepts utilised in three adaptations. Mark Haddon’s novel The Curious Incident of the Dog in the Night-Time (2003) forms the basis of Simon Stephens’ play of the same name (2012), which in turn resulted in productions directed by Marianne Elliott and Sara Brodie. Kit Williams’ picturebook Masquerade (1979) is expanded and reworked by Kate Mulvany in her play Masquerade (2015), which was given life on the stage in a production directed by Lee Lewis and Sam Armstrong. Mulvany interweaves song into her script, and this awareness of the musicality of theatre is amplified in Lisa Kron and Jeanine Tesori’s libretto Fun Home (2015), an adaptation of Alison Bechdel’s graphic memoir Fun Home: A Family Tragicomic (2006). By considering the play text, and each individual production, as an adaptation in its own right, the research presented here aims to foreground the place of theatrical adaptation in adaptation studies.