β-Crystalline phase gallium oxide (β-Ga 2 O 3 ) is an ultrawide bandgap material with prospective applications in electronics and deep ultraviolet (DUV) optoelectronics and optics. The monoclinic crystal structure of β-Ga 2 O 3 results in optical anisotropy to incident light with different polarization states. This attribute can lead to different optical applications in the DUV. In this article, we investigated the optical properties of β-Ga 2 O 3 thin films grown by pulsed laser deposition technique on sapphire substrates with different crystallographic orientations. Marked in-plane polarization anisotropy, determined by reflectance and Raman spectroscopy, was observed for β-Ga 2 O 3 films deposited on an r -cut sapphire substrate. In contrast, isotropic optical properties were observed in β-Ga 2 O 3 films deposited on a c -cut sapphire substrate.