The ATLAS experiment at the LHC has undertaken an extensive program to probe and characterize the hot and dense quark-gluon plasma created in relativistic heavy ion collisions and, in general, to study non-perturbative and collective properties of the strong interaction. In this report we summarize the most recent results on the collectivity in pp, p+Pb and nucleus-nucleus collisions, results on jets, quarkonia, heavy flavor and electroweak boson production, measured in Pb+Pb and p+Pb collisions.
This report covers also new results on electromagnetic processes studied in ultra-peripheral collisions.