氮氧化物指的是只由氮、氧两种元素组成的化合物。常见的氮氧化物：

其中除五氧化二氮常态下呈固体外，其他氮氧化物常态下都呈气态。作为空气污染物的氮氧化物（NO_x）常指NO和NO₂。

Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:

The compounds NO and NO₂ are radicals. In addition, there are several anions of nitrogen oxides. The most stable of these is the nitrate anion:

but other nitrogen oxoanions include nitrite, peroxonitrite, trioxodinitrate (hyponitrate), and nitroxylate.