市场失灵（英文：Market Failure）为微观经济学术语，系立基于竞争市场的运作所发生问题的经济理论。传统自由经济学者认为，一个社会中的供给与需求可以构成完全竞争市场。而完全竞争的经济状态，系指生产者追求利益极大化，而消费者追求效用极大化，而达到所谓「帕累托效率（Pareto efficiency）」的状态，即没有任何人的效用受损，资源分配获得最佳效率，价格像一双看不见的手（An Invisible Hand），主导市场内经济活动。

In economics, market failure is a situation in which the allocation of goods and services is not efficient. That is, there exists another conceivable outcome where an individual may be made better-off without making someone else worse-off. Market failures can be viewed as scenarios where individuals' pursuit of pure self-interest leads to results that are not efficient – that can be improved upon from the societal point of view. The first known use of the term by economists was in 1958, but the concept has been traced back to the Victorian philosopher Henry Sidgwick.