"Quantum interacting systems lie at the forefront of contemporary physics, posing challenges to our understanding of quantum phases, many-body dynamics, and a variety of condensed matter phenomena. Also, advances in quantum applications, including quantum computation and metrology, rely on interactions to create entanglement and to improve sensitivity beyond the standard quantum limit. In particular, the generation of large-scale, many-body entanglement in solid-state systems is a long-standing goal for many applications of quantum science.These outstanding problems attract substantial theoretical attention, leading to the development of remarkable techniques, ranging from renormalization group approaches to exact solutions in certain cases. However, in most cases it is necessary to resort to approximations and perturbative analysis. Thus in recent years tremendous effort has been invested into developing precision experimental tools to simulate many-body Hamiltonians, with realizations so far in cold atomic systems and trapped ions.Here we propose a complementary experimental approach using Nitrogen-Vacancy (NV) color centers in diamond as a quantum many-body spin simulator. The NV center is an atom-like spin defect in a robust solid, with remarkable optical properties and a long electronic spin coherence lifetime. NV-diamond has been applied successfully to magnetic field sensing and demonstrations of spin-based quantum information processing.The goal of this project is to advance this new paradigm of atomic-like spin defects in the solid state as a simulator for quantum many-body spin systems, offering a platform for creating long-range interactions, quantum spin phases, and quantum computing resources. This approach holds the promise to advance the state-of-the-art by providing powerful new tools for measurement and control, and a unique quantum test-bed lying between “clean” ultracold atomic systems and “dirty” condensed matter systems."