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We describe a scenario where the smallness of neutrino masses is related to a global symmetry that is only violated by quantum gravitational effects. Here, the coupling of neutrinos to gauge singlet right-handed fermions is attributed to symmetry preserving gravitational operators suppressed by the Planck mass. The proposed scenario leads to axion particles that decay into neutrinos, which could be probed through cosmological measurements and may help explain the Hubble parameter tension. The scenario could potentially provide axion dark matter candidates.