  In this paper the results of Higgs searches at the ATLAS experiment,
operating at the LHC, are summarised. The results are based on data samples
corresponding to an integrated luminosity of up to 20.7 fb-1 at a
centre-of-mass energy of 8 TeV and 4.6 fb-1 at 7 TeV. The observation of a
Higgs boson is established. The mass of the new boson is measured to be 125.5
+/- 0.2 (stat) +0.5-0.6 (syst) GeV, and the ratio of the observed number of
events and expected from a Standard Model Higgs Boson is compatible with unity,
mu = 1.30 +/- 0.13 (stat) +/- 0.14 (sys). The spin and parity properties as
well as the couplings structure are compatible with those predicted for a
Standard Model Higgs Boson. No evidence of further Higgs states is found.
