An exhaust gas turbocharger having a hydrodynamic plain bearing or a hydrodynamic plain bearing, comprising a rotor (10) and a counter-bearing part (50) assigned to the rotor (10), wherein a rotor bearing surface (17.1, 17.2, 17.3) of the rotor (10) and a counter-surface of the counter-bearing part (50) face each other to form a hydrodynamic plain bearing, wherein the rotor bearing surface and/or the counterface, when cut along and through the axis of rotation (R) in sectional view, form(s) a continuous bearing contour forming at least two contour sections (44.1 to 44.3; 53.1 to 53.3) to provide hydrodynamic load capacities in both radial and axial directions, and wherein the counter-bearing part (50) is mounted in a bearing housing (60) or housing part. In order to be able to provide such an exhaust gas turbocharger with a compact and efficient bearing arrangement having a hydrodynamic plain bearing, wherein at the same time the hydrodynamic plain bearing can be easily mounted with a small number of parts, provision is made according to the invention that in that a preferably circumferential gap area (57) for forming a trapped oil film is formed between an outer contour of the counter-bearing part (50) and the bearing housing (60) or the housing part, wherein the gap area (57) is spatially connected to a lubricant guide channel (61), and in that the gap area (57) and the continuous bearing contour of the rotor (10) and/or of the counter-bearing part (50) overlap at least sectionally in the direction of the axis of rotation (R).