Action research seeks to bring together action and reflection, theory and practice, in participation with others, in pursuit of practical solutions to issues of pressing concern to people. Action research is an invitation to looking, listening, and taking action with others in multiple ways. It is a research orientation that may include quantitative and/or qualitative methods. The action research paradigm is distinctive in three fundamental ways. First, it integrates first-person research on oneself, second-person research within a group, and integrates those with third-person research for larger collectivities. Second, it interweaves research and action, treating the researchers also as coactors, sometimes inviting them to share in the design of the research, often doing research and offering feedback in the very midst of action. Third, the aim of action research is not only (and not mainly) to describe empirical regularities in third-person data but rather to help individuals, teams, and wider institutions identify values worthy of pursuit and to feedback data that makes such pursuit more effective. Feedback through action research processes may generate not only incremental “single-loop” action corrections, but also “double-loop,” transformative changes in actors’ strategies and actions, as well as “triple-loop” realignments among actors’ purposes, strategies, actions, and outcomes. In this entry, contemporary exemplars are presented to help illustrate the integration of the subjective, intersubjective, and objective voices. Notes on the historical provenance of action research highlight that the spirit of action research has existed since Aristotle. Today’s practices interweave Kurt Lewin-inspired Northern Hemisphere action research with that of Paolo Freire-inspired Southern Hemisphere emancipatory action research. Glimpsing the global sustainability crisis, this entry situates action research as an increasingly popular way for conducting action-oriented transformations research.