High-entropy nanomaterials have been arousing considerable interest in recent years due to their huge composition space,unique microstructure,and adjustable properties.Previous studies focused mainly on high-entropy nanoparticles,while other high-entropy nanomaterials were rarely reported.Herein,we reported a new class of high-entropy nanomaterials,namely (Ta0.2Nb0.2Ti0.2W0.2Mo0.2)B2 high-entropy diboride (HEB-1) nanoflowers,for the first time.Formation possibility of HEB-1 was first theoretically analyzed from two aspects of lattice size difference and chemical reaction thermodynamics.We then successfully synthesized HEB-1 nanoflowers by a facile molten salt synthesis method at 1423 K.The as-synthesized HEB-1 nanoflowers showed an interesting chrysanthemum-like morphology assembled from numerous well-aligned nanorods with diameters of 20-30 nm and lengths of 100-200 nm.Meanwhile,these nanorods possessed a single-crystalline hexagonal structure of metal diborides and highly compositional uniformity from nanoscale to microscale.In addition,the formation of the as-synthesized HEB-1 nanoflowers could be well interpreted by a classical surface-controlled crystal growth theory.This work not only enriches the categories of high-entropy nanomaterials but also opens up a new research field on high-entropy diboride nanomaterials.