Ⅲ-nitride materials possess superior optical and electrical properties due to direct bandgap and polarization effects. Light-emitting devices are already common in daily lighting, traffic signage, landscape lighting, etc. Additionally, they hold promise for next-generation displays, e.g., microLED displays, as well as field effect transistors (FETs), for example, high electron mobility transistors (HEMTs) and p-channel FETs. The investigation of antipolar (N-polar) epitaxy and devices is also flourishing. The following Special Issue reprint gathers research achievements related to III-nitride materials and their associated devices, covering growth methods, device fabrication technology, structural design, and physical mechanisms of III-nitride semiconductors, devices, etc.