Background: Over the past several decades, understandings of civic knowledge and engagement have been enlarged in productive ways; the field has been transformed by contributions rooted in and showcasing critical, cultural, transnational, activist, and participatory approaches to the civic. Civic action research fits neatly amid these new articulations of the civic; multiple studies attest to its potential for creating civic learning experiences that build on young people's strengths and provide space for critical analysis and informed action. In this social design project, civic action research investigations conducted by youth in communities impacted by structural inequality catalyzed densely interwoven, affectively infused networks of cross-district interaction and action: critical ecologies of civic learning. Focus of Study: This article retheorizes civic learning in light of findings from a research initiative rooted in the question: "How might civic inquiry be used to create school district practices that nurture and integrate the civic voice of youth?" Research Design: In this 18-month-long social design collaboration between a university-based research team and two public school districts in the northeastern United States, youth in five participating schools--two high schools and three middle schools--carried out civic inquiry projects under the guidance of experienced social studies teachers. In these projects, young people examined their communities, selected issues to investigate, designed and carried out research, analyzed data, communicated findings, and took action. Data collected by the adult researchers included observations of club sessions, focus groups with students, interviews with adult stakeholders, and observations of "civic voice events" involving both youth and adults. Interdisciplinary, iterative reading and thematic coding led to the development of the conceptual framework that is the focus of this article. Conclusions or Recommendations: This article illustrates and theorizes "critical ecosystems of civic learning." In this project, civic learning was collectively produced rather than vertically transmitted--a joint activity of youth and adults. A historically and structurally situated phenomenon, civic learning was not separable from the resources, assets, and experiences that young people brought with them as civic actors. Civic learning was not bound by the container of the classroom--it moved and flowed across settings, accruing through the interactions of people inhabiting varied perspectives. Finally, civic learning was affective and relational, engaging emotion and fostering connection. Building upon and extending critical and participatory reframings, a critical ecosystems theorization of civic learning can help us to envision deeper, more expansive forms of civic education that support, activate, and empower young people from across a broad spectrum of communities, propelling us toward a more just and inclusive civic future.