This introductory note to the special issue on vulnerability and fieldwork provides a critical overview of how the concept of vulnerability has been employed in fieldwork literature and argues for a deeper exploration of its implications. Moving away from the notion of ‘vulnerable populations’ as the primary angle of approach, we emphasise that vulnerability is not a static trait but a dynamic and contextual experience. We then highlight its critical, albeit under-researched, role for knowledge production. Investigating the relevance of vulnerability across all stages of a field research process – from design to implementation to write-up – we demonstrate how vulnerability may serve as a lens to reflect on the ethics, methodologies and epistemic implications of fieldwork. Ultimately, this note serves as a unifying thread for the diverse contributions of the special issue, each offering unique perspectives on the manifold dimensions of vulnerability in qualitative research.