磺酰胺（Sulfonamide），又称磺胺，是磺酸衍生物之一，通式 -S(=O)₂-NH₂，是磺酸的酰胺衍生物。

这个词常用来指磺胺类药物，一类具有磺酰胺结构的药物。

实验室中可以通过磺酰氯（如对甲苯磺酰氯）与胺缩合制取磺酰胺。

In chemistry, the sulfonamide functional group (also spelt sulphonamide) is -S(=O)₂-NH₂, a sulfonyl group connected to an amine group. Relatively speaking this group is unreactive. The amine center is no longer basic. The S-N bond is cleaved only with difficulty. Because of the rigidity of the functional group, sulfonamides are typically crystalline. For this reason, the formation of a sulfonamide is a classic method to convert an amine into a crystalline derivative which can be identified by its melting point. Many important drugs contain the sulfonamide group.