Dinitrogen dioxide is an inorganic compound having molecular formula N2O2.

Many structural isomers are possible.

The covalent bonding pattern O=N–N=O (a non-cyclic dimer of nitric oxide (NO)) is predicted to be the most stable isomer based on ab initio calculations and is the only one that has been experimentally produced.

[1] In the solid form, the molecules have C2v symmetry: the entire structure is planar, with the two oxygen atoms cis across the N–N bond.

The O–N distance is 1.15 Å, the N–N distance is 2.33 Å, and the O=N–N angle is 95°.