The top quark is the heaviest particle in the Standard Model, and the only one with a mass larger than the Higgs boson mass. Therefore, it plays an important role in several scenarios Beyond the Standard Model. New physics may be found either by the observation of new processes involving top quarks - in which Standard Model top-quark processes are backgrounds - or indirectly by finding deviations of measured observables with respect to Standard Model predictions. In both cases, it is crucial to perform precision measurements of all top-quark processes, in the widest possible phase-space. The Large Hadron Collider has already produced about 380 billions top quarks in proton-proton collisions since the startup in 2009, and this unprecedented amount of Data lead to a wide range of measurements and searches. A selection of recent results by the ATLAS collaboration in the top-quark sector will be presented.