硝化是向有机化合物分子中引入硝基（－NO₂）的过程，硝基就是硝酸失去一个羟基形成的一价的基团。芳香族化合物硝化的反应机理为：硝酸的－OH基被质子化，接着被脱水剂脱去一分子的水形成硝酰正离子（nitronium ion，NO₂）中间体，最后和苯环行亲电芳香取代反应，并脱去一分子的氢离子。

在此种的硝化反应中芳香环的电子密度会决定硝化的反应速率，当芳香环的电子密度越高，反应速率就越快。由于硝基本身为一个亲电体，所以当进行一次硝化之后往往会因为芳香环电子密度下降而抑制第二次以后的硝化反应。必须要在更剧烈的反应条件（例如：高温）或是更强的硝化剂下进行。

Nitration is a general class of chemical process for the introduction of a nitro group into an organic chemical compound. More loosely the term also is applied incorrectly to the different process of forming nitrate esters between alcohols and nitric acid, as occurs in the synthesis of nitroglycerin. The difference between the resulting structure of nitro compounds and nitrates is that the nitrogen atom in nitro compounds is directly bonded to a non-oxygen atom, typically carbon or another nitrogen atom, whereas in nitrate esters, also called organic nitrates, the nitrogen is bonded to an oxygen atom that in turn usually is bonded to a carbon atom.