In organic chemistry, hydroxamic acids are a class of organic compounds having a general formula  bearing the functional group , where R and R' are typically organyl groups (e.g., alkyl or aryl) or hydrogen. They are amides () wherein the nitrogen atom has a hydroxyl () substituent. They are often used as metal chelators.
Common example of hydroxamic acid is aceto-N-methylhydroxamic acid (). Some uncommon examples of hydroxamic acids are formo-N-chlorohydroxamic acid () and chloroformo-N-methylhydroxamic acid ().