[en] Tungsten trioxide (WO₃) thin films are of great importance due to their promising applications in various electrochemical devices. The present investigations are aimed towards the study of optical properties of WO₃ thin films prepared by electron beam deposition technique and their dependence on growth condition. The films were grown onto well cleaned Indium Tin Oxide (ITO) coated glass substrates in an oxygen partial pressure of 2x10^-4 mbar and at different substrate temperatures varying from room temperature (RT) to 450 °C. The optical transmittance of the films decreased with increasing substrate temperature. The optical bandgap decreases from 3.284 to 2.94 eV with increase of substrate temperature ranging from RT to 450 °C. (author)