The ATLAS collaboration has recently gone public with a measurement of the Higgs boson mass by combining independent measurements in H → ZZ ∗ → 4ℓ and H → γγ decay modes using 140 fb −1 of protonproton collision data collected by the ATLAS detector during LHC Run 2 at a centre-of-mass energy of 13 TeV. Combined with the Run 1 ATLAS mass measurement, this result yields a Higgs boson mass of 𝑚H = [125.11 ± 0.09 (stat. ) ± 0.06 (syst. )] GeV = 125.11 ± 0.11 GeV, corresponding to a 0.09% precision achieved on this fundamental parameter of the Standard Model of particle physics. This measurement supersedes in terms of precision the result from CMS, 𝑚H = [125.38 ± 0.11 (stat. ) ± 0.08 (syst. )] GeV = 125.38 ± 0.14 GeV, performed in the same channels with the Run 1 and 2016 datasets. This talk intends to give an overview of this hot-of-the-press ATLAS result, discussing the key analysis techniques and systematic uncertainty mitigation measures, particularly for the measurement in the diphoton decay channel which have been performed with the Run 2 dataset for the first time. Finally the prospects of the same measurement from CMS with the full Run 2 dataset will be outlined.
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