A nitrate nitrite, or nitrite nitrate, is a coordination complex or other chemical compound that contains both nitrite () and nitrate () anions. They are mixed-anion compounds, and they are mixed-valence compounds. Some have third anions. Many nitrite nitrate compounds are coordination complexes of cobalt. Such a substance was discovered by Wolcott Gibbs and Frederick Genth in 1857.
Mercury(II) nitrate and potassium nitrate in water solution produce the salt tripotassium tetranitratomercurate(II) nitrate .
On heating, nitrate nitrites lose NO<sub>2</sub> and NO and yield metal oxides.
Other compounds having an element in two different anion states include the sulfate sulfites, the phosphate phosphites, arsenate arsenites and the selenate selenites.