This chapter draws upon the concept of strategic action fields to illustrate how different actors collaborate and compete in order to shape a social innovation field. From this perspective, actors seek to influence and change the objectives and power constellations within the field(s), effectively setting out the direction of travel for transformative social change. They achieve this, in part, through discursive strategies aimed at persuading others to their cause. We identify three different discourses that are shaping contemporary ideas of what social innovation is or ought to be. In our concluding section we set out four areas of future research that can shed light on social innovation fields as arenas of contestation.