  Searches for new resonances in the diphoton final state, with spin 0 as
predicted by theories with an extended Higgs sector and with spin 2 using a
warped extra-dimension benchmark model, are presented using 139 fb$^{-1}$ of
$\sqrt{s} = $ 13 TeV $pp$ collision data collected by the ATLAS experiment at
the LHC. No significant deviation from the Standard Model is observed and upper
limits are placed on the production cross-section times branching ratio to two
photons as a function of the resonance mass.
