Ultraviolet (UV) photo detectors have become essential for applications ranging from military and space exploration to environmental monitoring and secure communications. Traditional semiconductors such as silicon and GaN face limitations in achieving solar blindness, environmental stability, and cost-effective scalability. In contrast, metal oxide semiconductors—with their wide band gaps, chemical robustness, and highly tunable nanostructures—have emerged as promising candidates for next-generation UV sensing. This review highlights the role of nanostructure design and interface engineering in advancing metal oxide–based UV photo detectors. We examine how morphology, dimensionality, and defect states influence optical detection mechanisms, and how engineered interfaces—including Schottky contacts, heterojunctions, and hybrid architectures—enable improved responsivity, selectivity, and response speed. After presenting comparative performance benchmarks, we discuss emerging strategies such as alloying, hybrid integration, and flexible device architectures. Finally, we identify key challenges related to device stability, scalability, and reproducibility, and offer perspectives on the future of metal oxide nanotechnology for UV sensing.