The term social innovation has become popular as an umbrella concept describing an array of social programs and initiatives deserving attention. Unfortunately, this flurry of social innovation activity has, as of yet, not led to the development of a comprehensive theory of social innovation. This is a critical missing step if our aim is to enact public and private policies to develop, stimulate, and maximize social innovation. Tellingly, we have yet to agree on a definition: there is no unified sense of what social innovation is and what is it not. Without a clearer idea of cause and effects in social innovation, it will remain difficult to develop desirable interventions and scale them up. This paper is a first step to close this gap; our aim is to offer a theoretical framework which can easily be used in practice. We start by proposing a new definition of social innovation, characterizing it as a process encompassing the emergence and adoption of socially creative strategies, which reconfigure social relations in order to actualize a given social goal. This definition offers several advantages. First, by defining social innovation as a process aiming to bring about social change we avoid two main deficiencies of current definitions. First, we do not tautologically define social innovation as its own outcome. Second, we refrain from making it normative, which is important because we can easily envision a successful implementation of a social creative strategy that aims to improve social conditions and has successfully brought significant social chance, only to find that the outcome leaves the target population worse off. A second advantage of defining social innovation as a process is that it enables us to easily delineate between the main actors, their institutional environment, and the interactions between them. This foundational framework will enable researchers to develop hypotheses and test them while simultaneously providing a basis for policy makers to develop policies rooted in an understanding of cause and effect, analysis of bottlenecks, and a deepened appreciation as to where policy can or cannot have a positive impact.