Relic neutrinos are fundamental and predicted to have free streamed throughout the Cosmos, liberated just 1 second after the Big bang. This neutrino background is like the CMB and its mass density may be inferred by J-PAS from the abundance and clustering of galaxy clusters. THE J-PAS survey is by default ideally suited to detect ~100,000 clusters over a large fraction of the Northern sky to z~1, and to derive both accurate SED based redshifts and weak lensing masses. Measuring the neutrino mass through the statistical properties of galaxy clusters as a function of mass and redshift is one of the top science goals of the J-PAS project.