Social innovation addressing social, economic and environmental challenges are increasingly recognized as crucial drivers of social changes. However, the concept of social innovation remains vague. This paper builds a conceptual framework from an economic perspective: the main criterion for identifying a social innovation concerns the way the benefits generated by an innovation are distributed between the (private or public) innovator and society. We close the paper by an extensive discussion of the conceptual boundaries, the research agenda and the policy implications we can derive based on the Framework.