Nitrosylazide is a highly unstable nitrogen oxide, chemical formula N₄O, which can be synthesized via the following reaction of sodium azide and nitrosyl chloride at low temperatures:

Below -50 °C, nitrosylazide exists as a pale yellow solid. Above this temperature, it decomposes into nitrous oxide and molecular nitrogen:

• Cotton, F. Albert; & Geoffrey Wilkinson. Advanced Inorganic Chemistry. 6th ed. New York: John Wiley & Sons, 1999. ISBN 0-471-19957-5 Text located on p. 331.