Accurate UV light detection is a crucial component in modern optoelectronic technologies. Current UV photodetectors are mainly based on wide-bandgap semiconductors (WBSs), such as III–V semiconductors. However, conventional WBSs have reached a bottleneck of low integration and inflexibility. In this regard, low-dimensional WBSs, which have suitable UV absorption, tunable performance and good compatibility, are appealing for diversified UV applications. UV photodetectors based on low-dimensional WBSs have broad application prospects in imaging, communication, multispectral and/or weak light detection and flexible and wearable electronics. This Review focuses on the progress, open challenges and outlook in the field of UV photodetectors on the basis of low-dimensional WBSs. We examine how material design, dimensionality engineering and device engineering of WBSs can control their morphological structures and properties and attempt to clarify the interplay among material growth, device structure and application scenarios.