In this thesis I explore contemporary understandings and practices of sustainability. Based on an ethnographic study at Anuvelar Investments, a sustainable financial services organisation, I contribute to both the conceptual and strategic literature by drawing upon the theoretical resources of discourse theory. In doing so, I position sustainability as a discourse which has implications for how it can be conceptualised but also how it can be understood in practice. My overall questions relate to conceptualising the contested and contingent nature of sustainability, but also the role of subjectivity when understanding sustainability in practice. All of which, I later argue, contribute to the political role particular articulations of sustainability might play within society more broadly. First, I note the ambiguous and contested nature of sustainability as being unavoidable due to the nature of language and discourse and its construction within an antagonism between pro-financial and pro-social/environmental logics. I contribute a conceptualisation of sustainability as a discourse that is set boundaries as to what it means within a particular context. This contextual understanding of sustainability shows how the discourse excludes and includes certain elements but also modifies or quilts other concepts, positions and ideas. It does so, I argue, due to the ‘empty’ quality of sustainability as a discourse, standing as an open yet powerful concept that can align various different positions and ideas. Second, building upon an understanding of the ambiguous and contested nature of sustainability I explore instances of identification with sustainability at Anuvelar Investments. Such an exploration mobilises the concepts of fantasy and enjoyment to contribute an understanding of the affective character of sustainability. Based upon interview data and observations I point to the beatific and horrific fantasies that engage and disgust individuals at Anuvelar Investments. Although the beatific character of sustainability provides a source of enjoyment for many, the horrific fantasies that are concealed within and outside the discourse are deemed equally pertinent in the maintenance of a sustainable subject. In so doing, I contribute to and problematise the sustainability literature that calls for employee engagement with the values of sustainability. Third, I contribute to the debates within critical management studies (CMS) in reference to the empirical work produced in this thesis and the particular case study of Anuvelar Investments. In presenting a vignette from my ethnographic study at Anuvelar, I explore the many ways in which it is possible to critique certain practices performed at Anuvelar. However, drawing on the political theory of Chantal Mouffe and discourse theory more broadly I present a different approach to critique that seeks a more positive approach and a more productive platform for engagement. Overall this thesis provides an important contribution to an understanding of sustainability as a discourse within contemporary organisations. In addition to this, it puts forward an argument that queries whether sustainability should always be seen as hijacked by or coopted into capitalism. Instead, I propose that sustainability can in fact be a useful discourse from which to challenge the status quo, albeit dependent upon its articulation.