Action research is a relatively recent phenomenon in the field of English language teaching, having emerged in the literature predominantly since the late 1980s. In this article, I discuss the antecedents, definitions, processes, and purposes of action research in the field of English language teaching. Action research is also considered in relation to more established notions of basic and applied research. The current scope and nature of action research studies found in the literature are then analysed. The article concludes with a consideration of some of the challenges to the status of action research as a research methodology and the issues that will need to be addressed if action research by language teachers is to be sustainable.