Peroxynitrate (or peroxonitrate) refers to salts of the unstable peroxynitric acid, HNO<sub>4</sub>. Peroxynitrate is unstable and decomposes to nitrate and dioxygen.
No solid peroxynitrate salts are known. However, there is a report that the chemist Sebastian Moiseevich Tanatar produced sodium peroxynitrate octahydrate (NaNO<sub>3</sub>÷H<sub>2</sub>O<sub>2</sub>÷8H<sub>2</sub>O) by evaporating a solution of sodium nitrate and hydrogen peroxide until crystallisation begins and then mixing with alcohol to form crystals of the octahydrate.