Cyanogen is the chemical compound with the formula (CN)₂. Its structure is N≡C−C≡N. The simplest stable carbon nitride, it is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules are linear, and consist of two CN groups ‒ analogous to diatomic halogen molecules, such as Cl₂, but far less oxidizing. The two cyano groups are bonded together at their carbon atoms, though other isomers have been detected. The name is also used for the CN radical, and hence is used for compounds such as cyanogen bromide (Br−C≡N) (but see also Cyano radical). When burned at increased pressure with oxygen, it is possible to get a blue tinted flame, the temperature of which is about 4,800 °C (8,670 °F) (a higher temperature is possible with ozone). It is as such regarded as the gas with the second highest temperature of burning (after dicyanoacetylene).

Cyanogen is the anhydride of oxamide:

Oxamide is manufactured from cyanogen by hydration:

Cyanogen is typically generated from cyanide compounds. One laboratory method entails thermal decomposition of mercuric cyanide:

Or, one can combine solutions of copper(II) salts (such as copper(II) sulfate) with cyanides; an unstable copper(II) cyanide is formed which rapidly decomposes into copper(I) cyanide and cyanogen.

Industrially, it is created by the oxidation of hydrogen cyanide, usually using chlorine over an activated silicon dioxide catalyst or nitrogen dioxide over a copper salt. It is also formed when nitrogen and acetylene are reacted by an electrical spark or discharge.

For the two less stable isomers of cyanogen, the order of the atoms differs. Isocyanogen (or cyanogen cyanide) is ⁻C≡N⁺−C≡N. It has been detected in the interstellar medium.

Addition of disulfur dichloride to cyanogen gives 3,4-dichloro-1,2,5-thiadiazole.