无谓损失（Deadweight loss）又称死三角，指由于垄断定价（monopoly pricing）、政府税制等因素引起的生产者和消费者都得不到的那部分，使资源得不到最佳限度的分配。在经济学领域中，经济行为所产生出来的效力是用经济效率来衡量。经济效率与物理上的效率不同，经济学效率是指物品得到最有效的分配。

一个无谓的损失（也被称为超额负担或资源配置效率低下）时可能出现的平衡的商品或服务是不是帕累托最优的经济效率的损失。换句话说，任何人将有更多的边际收益超过边际成本是不买产品的人，或谁拥有更多的边际成本超过边际效益所购买的产品。

In economics, a deadweight loss (also known as excess burden or allocative inefficiency) is a loss of economic efficiency that can occur when equilibrium for a good or service is not achieved or is not achievable. Causes of deadweight loss can include monopoly pricing (in the case of artificial scarcity), externalities, taxes or subsidies, and binding price ceilings or floors (including minimum wages). The term deadweight loss may also be referred to as the "excess burden" of monopoly or taxation.