Axions are a well-motivated aspect of physics beyond the Standard Model, a natural dark matter candidate, and also a generic prediction of string theory. We explore a novel detection channel, using axion-induced dissociation of deuterons into their constituent neutrons and protons. An opportune target for this process is the now-concluded Sudbury Neutrino Observatory (SNO) experiment, which relied upon large quantities of heavy water to resolve the solar neutrino problem. From the full SNO dataset we exclude in a model-independent fashion isovector axion-nucleon couplings > 2 × 10−5/GeV at 95% C.L. for sub-MeV axion masses, covering previously unexplored regions of the axion parameter space. In the absence of a precise cancellation between axion-proton and axion-neutron couplings this result also exceeds comparable constraints from other laboratory experiments, and excludes regions of the parameter space for which astrophysical constraints from SN1987A and neutron star cooling are inapplicable due to axion trapping. Based on Phys.Rev.Lett. 126 (2021) no.9, 091601, arXiv:2004.02733.