AbstractCyclotron resonance is made on purest and deliberately Fe‐doped Cu2O to assess the extrinsic origin of one of the two polaron masses previously reported (0.58m0 and 0.69m0). Only one mass is observed, which shifts to higher values with doping and is excitation wavelength dependent, except for the best undoped material. The latter shows the lowest mass, ascribed therefore to the uppermost valence band. Material improvements are discussed with respect to the carrier lifetimes.