Heterodox economics refers to economic theories and communities of economists that are in various ways an alternative to mainstream economics. It is a multi-level term that refers to a body of economic theories developed by economists who hold an irreverent position vis-à-vis mainstream economics and are typically rejected out of hand by the latter; to a community of heterodox economists whom identify themselves as such and embrace a pluralistic attitude towards heterodox theories without rejecting contestability and incommensurability among heterodox theories; and to the development of a coherent economic theory that draws upon various theoretical contributions by heterodox approaches which stand in contrast to mainstream theory. Thus, this introduction to heterodox economics is organized as follows: the first section outlines the emergence of “heterodox economics” in the sense of a body of heterodox theories; the second deals with heterodox economics as a pluralist community of heterodox economists; the third section situates heterodox economics relative to mainstream economics; and the fourth section delineates heterodox economics in terms of theory and policy.