A search was performed for the decay of a Standard Model (SM) Higgs boson in the di-muon channel, using pp collision data recorded at sβ = 13 TeV with the ATLAS detector, corresponding to an integrated luminosity of 80.5 fbβ1. No significant excess of events was observed in the data. An observed (expected) upper limit at the 95% confidence level on the cross-section times branching ratio was set at 1.98 (2.13) times the SM expectation. The observed signal strength was measured to equal ΞΌsβ=β0.29β1.12+1.10β, corresponding to an observed (expected) significance of 0.00Ο (0.82Ο)