The top quark mass is measured in the tt¯→dilepton channel ( lepton=e,μ ) using ATLAS data recorded in the year 2012 at the LHC. The data were taken at a proton–proton centre-of-mass energy of s=8 TeV and correspond to an integrated luminosity of about 20.2 fb−1 . Exploiting the template method, and using the distribution of invariant masses of lepton– b-jet pairs, the top quark mass is measured to be mtop=172.99±0.41 (stat)±0.74 (syst) GeV , with a total uncertainty of 0.84 GeV . Finally, a combination with previous ATLAS mtop measurements from s=7 TeV data in the tt¯→dilepton and tt¯→lepton+jets channels results in mtop=172.84±0.34 (stat)±0.61 (syst) GeV , with a total uncertainty of 0.70 GeV .