Sodium arsenate is the inorganic compound with the formula Na₃AsO₄. Related salts are also called sodium arsenate, including Na₂HAsO₄ (disodium hydrogen arsenate) and NaH₂AsO₄ (sodium dihydrogen arsenate). The trisodium salt is a white or colourless solid that is highly toxic. It is usually handled as the dodecahydrate Na₃AsO₄^.12H₂O.

The compound can be obtained by neutralizing arsenic acid:

The salt (as its dodecahydrate) is isomorphous with trisodium phosphate. The anion AsO₄^3- exists at high pH, but below pH 11.5, it converts to HAsO₄^2- (also written HOAsO₃^2-).