A turbine of an organic Ranking cycle (ORC) is described. The turbine includes a shaft supported by at least two bearings and a plurality of axial stages of expansion, defined by arrays of stator blades alternated with arrays or rotor blades. The rotor blades are sustained by corresponding supporting disks. A main supporting disk is directly coupled to the shaft in an outer position with respect to the bearings, and the remaining supporting disks are constrained to the main supporting disk, and one to the other in succession, but not directly to the shaft. Some of the remaining supporting disks are constrained to the main supporting disk and cantileverly extend from the same side of the bearings that support the shaft, so that the center of gravity of the rotor part of the turbine is shifted more towards the bearings.