H2V3O8/GaN n-n heterojunction ultraviolet photodetectors are fabricated via a facile dip-coating method. The Schottky junction between the GaN and H2V3O8 builds a built-in electric field to achieve the self-powered phenomenon. The photodetector presents a high photocurrent (0.23 μA) and a fast response speed (less than 0.3 s) at 0 V bias and under 365 nm light illumination (24.50 mW cm-2). Furthermore, the photocurrent increases steadily as the light intensity increases from 0.53 to 24.50 mW cm-2. The H2V3O8/GaN heterojunction holds great potential to realize high-performance hybrid PDs.