平黄经是在太空动力学或天体力学中，天体在 轨道倾角为0的假想圆轨道上运动的黄经值。平黄经对时间的变化是一个常数，只有在近心点与远心点的值会与真黄经相同。

平黄经可以由下式计算：

此处：

Mean longitude is the ecliptic longitude at which an orbiting body could be found if its orbit were circular and free of perturbations. While nominally a simple longitude, in practice the mean longitude is a hybrid angle.