In the present work, Gallium Oxide (Ga2O3) were deposited as thin films by radio frequency (RF) magnetron sputtering at 300 °C substrate temperature on glass substrate using Ga2O3 target with 99.99% purity. The crystalline structure, morphology, optical properties of the Gallium Oxide films were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Visible Spectrometry, respectively. Experimental results show that annealing has an important role in the changes observed in the characterization of the Gallium Oxide thin films. All thin films produced were amorphous, except for the annealed P4-500. SEM pictures reveal the morphology of prepared Gallium Oxide thin films. The refractive index and real part of complex dielectric constant increased as the film deposition pressure increased.