The top quark is the heaviest elementary particle and unique among the known quarks since it decays before forming hadronic bound states. This makes measurements of the top quark itself particularly interesting as one can access directly the properties of a bare quark. The latest measurements of these properties with the ATLAS detector are reported using data from 8 TeV and 13 TeV proton-proton collisions at the Large Hadron Collider at CERN. The latest measurements of the top quark mass using template methods, as well as others aiming to measure the mass in a well-defined scheme, are presented. In addition, measurements for the top quark decay width, top quark spin observables and [Formula: see text]-boson helicity in events with top quark pairs ([Formula: see text]) are presented and compared to the Standard Model predictions. The cross-section measurements of top quark pair production in association with a photon, [Formula: see text]- or [Formula: see text]-boson are also reported and compared to the most accurate theoretical calculations. These measurements probe the top quark electroweak couplings. Limits on the rate of flavour-changing neutral current processes in the production or decay of the top quark are also shown.