In a first approach, ontic structural realism (OSR) is a realism towards physical structures in the sense of networks of concrete physical relations, without these relations being dependent on fundamental physical objects that possess an intrinsic identity as their relata. In that vein, OSR has been developed in recent years as a metaphysics of contemporary fundamental physics, mainly non-relativistic quantum mechanics (QM), relativistic quantum field theory (QFT) and the general theory of relativity (GTR). The fundamental physical features of permutation invariance in many-particles quantum theory (Muller 2009), quantum entanglement in QM (Esfeld 2004) and in QFT (Lam 2010a), gauge invariance in quantum gauge theories (Lyre 2004) as well as background independence and gauge-theoretic diffeomorphism invariance in GTR (Rickles 2006; Esfeld and Lam 2008) have all been shown to support OSR in the following sense: these fundamental physical features can with good reason be taken to suggest all the same conclusion, namely that the fundamental physical objects – whatever they are according to the theory under consideration – are parts (relata) of a physical structure in the sense of a network of concrete physical relations. These objects do not have any existence – and in particular not any identity – independently of the structure they are part of (that is, the relations they bear to each other).