Top quark mass measurement with ATLAS

The LHC will be the first top quark factory. ttbar pairs will be produced at such a high rate that statistical error on the top quark mass measurement will soon become negligible. A precise top quark mass measurement is of fundamental importance for LHC experiments because it is one of the fundamental parameter of the Standard Model and because, during the LHC start-up, it will be a high mass reference candle. In the ATLAS experiment, the most promising analysis will use ttbar pairs that decay semi-leptonically. The different step of this analysis will be detailed and a quick overview of the other ongoing analyses will be given.