Ga₂O₃ with a suitable bandgap width is emerging to be a novel candidate for future optoelectronic applications in the solar-blind region (<280 nm). Herein, solar-blind photodetectors are developed by combining layered GaSe flakes with Ga₂O₃ epitaxial films, forming a van der Waals pn heterojunction. Photoresponse characterizations indicate that the GaSe/Ga₂O₃ pn junction is highly sensitive to solar-blind ultraviolet light, with the maximum sensitivity at ∼255 nm. The photodetector demonstrates a particularly high responsivity of 51.9 A/W, a pronounced specific detectivity up to 10¹⁴ Jones, and a fast response speed of ∼0.3 ms under ultraweak light illumination. These figures of merit are significantly superior to most of the reported Ga₂O₃-based photodetectors. This work reveals the great potential of GaSe/Ga₂O₃ van der Waals heterojunction for developing next-generation, solar-blind photodetectors.