We present a universal information-capacity bound (UICB) that constrains the structural complexity and stability of finite quantum systems independently of their microscopic dynamics. Based on an operator-algebraic formulation using C*-algebras and the CCR/Weyl algebra, the bound establishes a maximal admissible information load I_max, limiting the internal relational complexity of any finite quantum configuration. When the structural complexity C_phys approaches this threshold, the system becomes unstable or ceases to admit a consistent quantum state, providing a unified explanation for collapse phenomena, fragmentation, and drip-line behavior. The UICB yields concrete, falsifiable predictions across several domains: (i) termination of neutron drip-lines in medium and heavy nuclei, (ii) collapse thresholds in bosonic condensates, (iii) saturation of configurational complexity in amorphous solids, and (iv) limits on global entanglement growth in quantum networks. These predictions offer experimentally testable signatures for validating or refuting the universality of the bound. This work proposes a structural, model-independent constraint that complements and extends existing theoretical frameworks in nuclear physics, many-body quantum systems, and quantum information theory.