This issue elaborates upon the notion of singularity, bringing together approaches from social sciences, philosophy and the arts, operating in two ways. First, we consider analytic operations that produce generalizing and comparable knowledge from objects deemed singular, unique, irreducible, contingent. While remaining in the continuity of the founding debates in the social sciences on the articulation of representativity and "limit cases", the various articles of the issue extend these debates on new bases, taking inspiration from philosophy, law or the arts. The second, more empirical, point from which we consider singularity is that of concrete processes of individual singularization, based on practices, interactions and sociabilities in various fields (political representation, activist engagement and the use of law, artistic and cultural practices, aesthetic practices of the body, neighborhood sociability). The aim here is to analyze, case by case, the logics of the construction of singular identities in individuals, and to understand how they interact with social determinations.