International audience Design can be said "social" in various ways. The first appears when one considers that, unlike those who are born from Art, forms that arise from Design always have a use value and, therefore, a social impact. They are placed on the market to meet the needs of the users and they circulate in different areas of the everyday life. Although this is not its primary purpose, Industrial Design has always had such a significant social impact by changing our lifestyles and creating between objects and us emotional relationships. In this first case, Design can be said "social" by accident, that is to say involuntarily. The second way to consider the social dimension of design occurs when designers openly claim that the primary purpose of their work is a social purpose, voluntarily assumed. Contrary to what is suggested by the current development of "social innovation," this view is not recent or new. It has existed since the origins of the discipline and throughout the history of it, from William Morris to Victor Papanek. However, if it grows more and more today, it is because it tends to gradually become the founding principle of a new discipline which claims the name of "Social Design ». The purpose of this paper is to try to identify the contours of this new discipline by trying to give a theoretical definition supported on emerging project practices. To do this, we must first wonder whether the characterization of Design as "social" is a tautology or not. Indeed, in a previous work, we proposed the idea that every design has basically a "socioplastic effect" (Vial 2010). By this, we mean that the designer, because he works on uses, necessarily works also on shaping the social. And this seems so true that we can consider the social dimension of design as one of the main criteria of demarcation between Design and Art. For sure, Art also has a social dimension like in Pop Art, Street Art, etc. But we state that Art is social by contingency while Design is social by necessity. Paola Antonelli from the MoMA well said recently : "An artist can choose whether to be responsible towards other human beings or not, but instead a designer has to be, by definition ». Design is social by definition. Therefore, what is meant by "Social Design »? Is Social Design a new branch of design or does it repeat the intrinsic social purpose of every Designer’s gesture? Our hypothesis is the following: Social Design is a contemporary attempt to separate a new kind of design from the traditional market-centered industrial design. This attempt aims to organize a new design expertise whose goal is "to act in favour of society" by directing the "unique power of design toward serving the greater good" (Tromp 2013). This paper will conclude by a definition of Social Design based on two sample projects.