五氧化二铌，化学式Nb₂O₅。

白色粉末。不溶于水，难溶于酸，可溶于熔融硫酸氢钾或碱金属碳酸盐和氢氧化物中。

Niobium pentoxide is the inorganic compound with the formula Nb₂O₅. It is a colourless insoluble solid that is fairly unreactive. It is the main precursor to all materials made of niobium, the dominant application being alloys, but other specialized applications include capacitors, lithium niobate, and optical glasses.