Group III-nitride nanowires have attracted a lot of research interest in the past decade. They contain both the intrinsic properties of III-nitride materials and some unique properties induced by the nanowire structures. This article reviews the growth methods to obtain III-nitride nanowires, and discusses the pros and cons of both top-down and bottom-up approaches, with detailed discussions on different epitaxy methods. The most widely used catalyst-induced epitaxy and extrinsic particle free epitaxy to grow III-nitride nanowires are compared. The properties of those nanowires make them promising candidates for a broad range of applications, including optoelectronic, electronic and electromechanical devices, which are also presented, with a focus on the current challenges and recent progresses.