Two-dimensional (2D) semiconductors are limited to graphene analogues of layered materials, so it is extremely challenging to fabricate 2D non-layered materials with thicknesses of only a few atomic layers. Here, we report the successful fabrication of 2D Ga2O3 from the corresponding GaSe nanosheets and a solar blind photodetector based on 2D Ga2O3. The as-prepared 2D β-Ga2O3 is polycrystalline and has a thickness of less than 10 nm. Furthermore, we demonstrate a photodetector based on 2D β-Ga2O3, which show a sensitive, fast and stable photoresponse to ultraviolet radiation (254 nm). The responsivity, detectivity and external quantum efficiency of the photodetector are 3.3 A W−1, 4.0 × 1012 Jones and 1600%, respectively, indicating that the 2D Ga2O3 has great potential for application for solar-blind photodetectors.