<p>Polyradical nanographenes featuring strong spin entanglement and robust many-body spin states against external magnetic perturbations not only enable the exploration of correlated quantum magnetism at the molecular scale, but also constitute promising candidates for developing molecular qubits with chemical tunability and building scalable quantum networks. Here we use a predictive design strategy to realize the on-surface synthesis of two homologues of Clar’s goblet, C₆₂H₂₂ and C₇₆H₂₆, via lateral and vertical extensions of the parent structure, respectively. Vertical extension increases the number of topologically frustrated zero-energy modes, which scales linearly with the total number of benzene-ring rows. By contrast, lateral extension enhances electron–electron interactions, leading to the emergence of additional radical states beyond those predicted by the topological zero-energy modes. Consequently, both structures exhibit correlated tetraradical character and a many-body singlet ground state, as confirmed by multireference theoretical calculations. These magnetic states arise from unique magnetic origins and also display distinct resilience to external perturbations, as experimentally validated using nickelocene-functionalized scanning probe techniques. Our work presents a general strategy for the rational design of highly entangled polyradical nanographenes with tunable spin numbers and resilience of many-body spin states to perturbations, opening up exciting possibilities for exploring correlated spin phases in molecular systems and advancing quantum information technologies.</p><p></p>