钨酸，是三氧化钨（WO₃）各种水合物形态的总称。其最简单的形态，一水合钨酸，化学式为WO₃·H₂O，另一个常见形态为二水合钨酸，WO₃·2H₂O。

黄色粉末。加热至100°C时失去一分子水而转变为三氧化钨。几乎不溶于酸，微溶于热水，溶于碱、氢氟酸和氨水。

Tungstic acid refers to hydrated forms of tungsten trioxide, WO₃. The simplest form, the monohydrate, is WO₃·H₂O, the dihydrate WO₃·2H₂O is also known. The solid state structure of WO₃·H₂O consists of layers of octahedrally coordinated WO₅(H₂O) units where 4 vertices are shared. The dihydrate has the same layer structure with the extra H₂O molecule intercalated between the layers. The monohydrate is a yellow solid and insoluble in water. The classical name for this acid is 'acid of wolfram'.