维里定理（英语：Virial theorem，又称位力定理，均功定理）是描述稳定的自引力体系的一个定理，其数学表示是：

其中T是系统内部的总动能，W是系统的总引力势能。对于具有磁场和自转的稳定体系，维里定理表示为：

其中T_r是系统转动的动能，E_m是系统的总磁能。

量子力学中，当体系处于定态下，粒子动能的平均值的二倍等于粒子位矢点乘势能的梯度的平均值。

In mechanics, the virial theorem provides a general equation that relates the average over time of the total kinetic energy, , of a stable system consisting of N particles, bound by potential forces, with that of the total potential energy, , where angle brackets represent the average over time of the enclosed quantity. Mathematically, the theorem states