Nitrosyl fluoride (NOF) is a covalently bonded nitrosyl compound.

The compound is a colorless gas, with bent molecular shape. The VSEPR model explains this geometry via a lone-pair of electrons on the nitrogen atom.

Nitrosyl fluoride is typically produced by direct reaction of nitric oxide and fluorine, although halogenation with a perfluorinated metal salt is also possible. The compound is a highly reactive fluorinating agent that converts many metals to their fluorides, releasing nitric oxide in the process:

For this reason, aqueous NOF solutions are, like aqua regia, powerful solvents for metals.

Absent an oxidizable metal, NOF reacts with water to form nitrous acid, which then disproportionates to nitric acid:

These reactions occur in both acidic and basic solutions.

Nitrosyl fluoride also forms salt-like adducts with Lewis-acidic fluorides; for example, BF₃ reacts to give NOBF₄. Similarly, the compound nitrosylates compounds with a free proton; thus alcohols convert to nitrites:

Nitrosyl fluoride is used as a solvent and as a fluorinating and nitrating^{[dubious – discuss]} agent in organic synthesis.^{[citation needed]}