平均运动，是表征一颗卫星绕其椭圆轨道运行速度的物理量。除了轨道是正圆形外，平均运动都是一个平均值，并不能反映出即时的角速率。

在卫星轨道参数中，平均运动的单位一般为“周期/天”。

其中

• 为引力常量。
• 及为绕行天体的质量。
• 为半长轴。

In orbital mechanics, mean motion (represented by ) is the angular speed required for a body to complete one orbit, assuming constant speed in a circular orbit which completes in the same time as the variable speed, elliptical orbit of the actual body. The concept applies equally well to a small body revolving about a large, massive primary body or to two relatively same-sized bodies revolving about a common center of mass. While nominally a mean, and theoretically so in the case of two-body motion, in practice the mean motion is not typically an average over time for the orbits of real bodies, which only approximate the two-body assumption. It is rather the instantaneous value which satisfies the above conditions as calculated from the current gravitational and geometric circumstances of the body's constantly-changing, perturbed orbit.