地球椭球也称地球椭球体，是在大地测量学、天文学和地球科学等领域中所使用的地球形状的数学表示。参考椭球体就是一种具有一定几何参数的地球椭球。近两百年来，科学家利用大地测量和重力测量的资料，求算出多组地球椭球参数。下表是比较常用的几个：

An Earth ellipsoid is a mathematical figure approximating the shape of the Earth, used as a reference frame for computations in geodesy, astronomy and the geosciences. Various different ellipsoids have been used as approximations.

It is an ellipsoid of revolution, whose short (polar) axis (connecting the two flattest spots called geographical north and south poles) is approximately aligned with the rotation axis of the Earth. The ellipsoid is defined by the equatorial axis a and the polar axis b; their difference is about 21 km or 0.335 percent. Additional parameters are the mass function J2, the correspondent gravity formula, and the rotation period (usually 86164 seconds).