A combination of searches for Higgs boson pair production is performed using up to 139fb-1 of proton-proton collision data at a center-of-mass energy √s = 13 TeV recorded with the ATLAS detector at the LHC. The combination exploits three analyses searching for HH decays to bbyy, bbtautau and bbbb. Results are interpreted in the context of non-resonant and resonant Higgs boson pair production scenarios. In the non-resonant interpretation, upper limits are set on the Higgs boson pair production cross-section and on the self-coupling modifier κ_lambda. In the resonant interpretation, upper limits are set on the resonant Higgs boson pair production cross-section as a function of the heavy resonance mass.