Creating a long‐lasting impact is one of the defining goals of social entrepreneurship. Yet, social entrepreneurs often face a dilemma between sustaining their organization and offering a permanent fix to a social problem. We question the assumption that organizational permanence and growth are intrinsically desirable for social entrepreneurs and propose an alternative, an inductively grounded model of ecosystem leadership, which we term ecosystem catalysis. Through a single case study of social entrepreneurs addressing the lack of access to diarrhoea treatment in Zambia, we conceptualize ecosystem catalysis as a process through which an organization forms an ecosystem around a new value proposition while gradually making itself redundant, ultimately withdrawing from the ecosystem without compromising its functioning. Our work contributes to ecosystem literature by contrasting the key aims and mechanisms of an ecosystem catalyst to those of an orchestrator and identifying the conditions under which catalysing may be a better choice than orchestrating an ecosystem. We contribute to social entrepreneurship literature by decoupling social impact from organizational growth and permanence and presenting a more dynamic model of social impact resulting from distributed contributions in ecosystems.