This note presents a search for new resonances decaying into a boson and a 125~ GeV Higgs boson in the and final states, where or , in collisions at \sqrt{s}=13~TeV. The data used correspond to a total integrated luminosity of 139~\ifb\ collected by the ATLAS detector during Run-2 of the Large Hadron Collider. The search is conducted by examining the reconstructed invariant or transverse mass distributions of candidates for evidence of a localised excess in the mass range from 300~{GeV} to 5~{TeV}. No significant excess is observed and confidence level upper limits between 1~pb and 0.4~fb are placed on the production cross-section times branching fraction of resonances in heavy-vector-triplet models and the CP-odd scalar boson in two-Higgs-doublet models.}