消毒（Disinfection）是利用化学品或其他方法消灭大部份微生物，使常见的致病细菌数目减少到安全的水平。然而，与杀菌（Sterilization）相比，部份细菌孢子、过滤性病毒、肺结核菌及真菌等都可能没有消灭。

消毒剂通常用于日常生活所接触的事物，如地板、餐具，在医疗上则只可用于一些体外的工具（如探热针）。

消毒的方式一般可使用酒精、甲醛、氨水、漂白水、碘液等常用消毒剂进行喷洒擦拭乃至清洗，甚至简单的沸水浸洗和蒸煮，也有使用紫外光照射进行消毒等。

Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than sterilization, which is an extreme physical and/or chemical process that kills all types of life. Disinfectants are different from other antimicrobial agents such as antibiotics, which destroy microorganisms within the body, and antiseptics, which destroy microorganisms on living tissue. Disinfectants are also different from biocides — the latter are intended to destroy all forms of life, not just microorganisms. Disinfectants work by destroying the cell wall of microbes or interfering with the metabolism.