Literary texts that come to be recognised as great challenge literary conventions of their times and necessitate or anticipate the transformation of critical paradigms. Such texts are often misunderstood and miscategorized by their contemporary critics. The texts of the Irish writer, Brian O’Nolan (1911-66), fall into this category, as they occupy a unique position between the modernist and postmodern literary paradigms. In my thesis I will explore how O’Nolan’s writings – both his fiction and non-fiction – re-imagine the role of the author challenging, pointing beyond its modernist conceptualisation. The first chapter will examine how this multifaceted artist destabilised what Michel Foucault called “the author function” by writing under proliferating pseudonyms. The second chapter will focus on O’Nolan’s first novel, At Swim-Two-Birds, published under the pseudonym, Flann O’Brien, especially on the author characters multiplying in a mise-en-abyme narrative structure and their relation to modernist and postmodernist conceptions of authorship. The third chapter will further highlight the postmodern challenge to the authority of the author in the novel by exploring the relationship between the author figures and their characters.