Mainstreaming Sustainability: Integration Within Business-as-Usual or Transformative Change?

We introduce this Special Issue on Mainstreaming Sustainability by reviewing insights from organisational research on how sustainability becomes, or fails to become, mainstream practice. Although organisational sustainability research has investigated diverse approaches to addressing sustainability challenges, critical questions about mainstreaming remain underexplored. To advance this field of research, we define sustainability mainstreaming and identify two distinct types: integrating sustainability within business‑as‑usual and transformative change. We offer a novel framework of sustainability mainstreaming that integrates multiple levels of analysis, organises research across these levels, and identifies the mechanisms that explain why the process of mainstreaming reproduces business-as-usual in some contexts while enabling transformative change in others. We position the eight Special Issue articles within this framework, distinguishing business‑as‑usual and transforming modes of mainstreaming at the institutional, interorganisational, organisational, and individual levels. We conclude with a research agenda on four themes: multilevel integration, the impact of mainstreaming, temporal complexity, and political realities.