<p>The conceptualization of agency for the purpose of sustainability transformations research remains a pivotal yet elusive subject, requiring to capture the inherent interactive complexity of the agent’s individual attributes and their socio-material embeddedness while providing enough clarity for empirical applicability. While significant advancements have been made in conceptualizing agency in recent years, the discourse has been characterized as scattered, using inconsistent terminology and drawing on ambiguous analytical lenses. This paper addresses these issues by providing a systematic-narrative review of the literature up to the year 2023 around concepts of agency in sustainability transformations research. On the basis of 157 included articles, three central conceptual claims are made to bring the debate forward: <i>First</i>, seven questions on agency are put forward as a theoretical tool to structure both past and future debate on agency, discussing the state of the art of definition, source of agency, relationships to transformative change, structure, power, determinants of actions’ qualitative characteristics as well as theoretical foundations. <i>Second</i>, a typology of prototypical perspectives on agency is proposed, distinguishing between singular, embedded, and relational/emergent agency approaches. <i>Third</i>, drawing on insights from the systematic literature review as well as from discussions in sociology, it is suggested to bring particularly singular and embedded agency perspectives constructively together by conceptualizing agency as the situated capability of an agent to perform intentional action (as a result of some reflective deliberation) with/within specific spatio-temporal contexts.</p>