This exploratory qualitative research analyses the concept and role of the Expert By Experience (EBE), and their relationship with Irish mental health policy and practice. Informed by a combined Foucauldian/Gramscian theoretical framework, the research critically analyses Irish mental health policy and practice through the lens of power-knowledge and hegemony (Gramsci, 1971). This critical analysis identifies how power-knowledge (Foucault, 1977) has traditionally been exercised in Irish mental health policy and practice, and which institutions and actors have been included in and excluded from its exercise. Power-knowledge is found to have primarily been exercised by the medical and statutory stakeholder spheres, through the functions and apparatus of the biomedical model of mental illness. The social model of disability and the biopsychosocial model of mental health are also found to be influential. A Vision for Change (Government of Ireland, 2006) espoused a biopsychosocial model of mental health, and is found to be the only piece of Irish mental health legislation not drafted from a biomedical perspective. A gap is identified in service-user inclusion in Irish mental health policy and practice. Through the parallel research strands of autoethnography and in-depth EBE interviews with five EBEs, the views, experiences, and insights of EBEs on Irish mental health policy and practice are gathered and thematically analysed. This analysis identifies a distinct journey taken by respondents in becoming EBEs, distinguished by the novel ‘step’ of ‘individual professionalisation’. An EBE stakeholder sphere in Irish mental health policy and practice comprised of EBEs who possess the distinct ‘dual’ traditional and experiential expertise gained through ‘individual professionalisation’ is proposed to address the gap in service-user inclusion in Irish mental health policy and practice. The research’s autoethnographical methodology, and its exploration of how individuals with subjugated knowledges have legitimised (Weber, 1922) their expertise, hold global implications for methodologies and knowledge generatio