公平理论（英语：Equity Theory），又称社会比较理论，是由美国心理学家约翰·斯塔希·亚当斯（John Stacey Adams）在《工人关于工资不公平的内心冲突同其生产率的关系》（1962，与罗森鲍姆合写）、《工资不公平对工作质量的影响》（1964，与雅各布森合写）、《社会交换中的不公平》（1965）等著作中提出来的一种激励理论。该理论侧重于研究工资报酬分配的合理性、公平性及其对职工生产积极性的影响，指出员工的激励程度来源于对自己和参照对象（Referents）的报酬和投入的比例的主观比较感觉。

Equity theory focuses on determining whether the distribution of resources is fair to both relational partners. Equity is measured by comparing the ratio of contributions (or costs) and benefits (or rewards) for each person. Considered one of the justice theories, equity theory was first developed in 1969 by J. Stacy Adams, a workplace and behavioral psychologist, who asserted that employees seek to maintain equity between the inputs that they bring to a job and the outcomes that they receive from it against the perceived inputs and outcomes of others (Adams, 1969). The belief is that people value fair treatment which causes them to be motivated to keep the fairness maintained within the relationships of their co-workers and the organization. The structure of equity in the workplace is based on the ratio of inputs to outcomes. Inputs are the contributions made by the employee for the organization.