偏硼酸（化学式：HBO₂），白色粉末，可溶于水，易溶于盐酸。自然界有偏硼酸存在。偏硼酸加热至300°C脱水生成三氧化二硼，通常由硼酸加热脱水制成，一般可用于搪瓷和制硼玻璃等。

Metaboric acid is the name for a family of inorganic compounds formed by the dehydration of boric acid. Metaboric acids are colourless solids with the empirical formula HBO₂. There are three forms of metaboric acid, all are white solids. One form of metaboric acid is molecule, and another forms are polymers.