Two dimensional boron nanosheets have been proposed theoretically for a decade, but were not experimentally synthesized until very recently. Research into their fundamental properties and device applications has since seen exponential growth. In this perspective, we review recent research progress related to 2D boron sheets, touching upon the topics of fabrication, properties, and applications, as well as discussing challenges and future research directions. We highlight the intrinsic electronic and mechanical properties of boron sheets, resulting from their diverse structures. Their facile fabrication and novel properties have inspired the design and demonstration of new nanodevices; however, further progress relies on resolving technical obstructions, like non-scalable fabrication techniques. We also briefly describe some feasible schemes that can address the associated challenges. It is expected that this fascinating material will offer tremendous opportunities for research and development in the foreseeable future.