异羟肟酸（英语：Hydroxamic acid），也称酰基羟胺，是具有-C(=O)-NH-OH结构的化合物，具弱酸性。可通过用醛为原料发生Angeli-Rimini反应，或以羟胺为原料制备：

异羟肟酸容易水解为羧酸和羟胺，可发生Lossen重排反应生成异氰酸酯：

异羟肟酸及衍生物可用作螯合剂、矿物浮选剂及用于鉴定金属离子。

A hydroxamic acid is a class of organic compounds bearing the functional group RC(O)N(OH)R', with R and R' as organic residues and CO as a carbonyl group. They are amides (RC(O)NHR') wherein the NH center has an OH substitution. They are often used as metal chelators.