Combination of the top-quark mass measurements from the Tevatron and from the LHC colliders

I present here the results for the combination of the top-quark mass (mt) measurements at the Tevatron and at the LHC. These combinations are based on measurements using up to 5.8 fb-1 from CDF and D0 yielding mt=173.18 +- 0.56(stat) +- 0.75(syst) GeV, and up to 4.7 fb-1 from ATLAS and CMS leading to mt=173.3 +-0.5(stat) +-1.3(syst) GeV.