行星定位仪 (复数：equatoria) 是一种天文的计算仪器，可以不用计算，使用几何模型就可以寻找月球、太阳、和行星等给定天体的位置。

现存最早的纪录是第五世纪的希腊哲学家蒲洛克勒斯的太阳定位仪，本质上它提供了说明如何建构一个木质或青铜的。 虽然古希腊人可能也会制作行星定位仪，第一个尚存的叙述是来自Libros del saber de astronomia (天文学知识之书)，在阿方索十世 (卡斯蒂利亚) 的赞助下，于十三世纪以西班牙文编译收集的天文作品，其中也包含了翻译自十一世纪的Ibn al‐Samḥ和阿尔扎切尔 两位阿拉伯文的文集。诺法拉的康潘纳斯 (c. 1261-1264)的行星定位仪的理论叙述了行星定位仪的构造，是欧洲已知最早的拉丁文著作。众所周知，理乍得·沃林福德 (1292–1336) 建造了名为阿尔比恩的先进的行星定位仪，可以计算月球、太阳和行星的经度。不同于其他的行星定位仪， 阿尔比恩可以预测食。

An equatorium (plural, equatoria) is an astronomical calculating instrument. It can be used for finding the positions of the Moon, Sun, and planets without calculation, using a geometrical model to represent the position of a given celestial body.

The earliest extant record of a solar equatorium, that is, one to find the position of the sun, is found in Proclus's fifth-century work Hypostasis, where he gives instructions on how to construct one in wood or bronze. Although planetary equatoria were also probably made by the ancient Greeks, the first surviving description of one is from the Libros del saber de astronomia (Books of the knowledge of astronomy), a Castilian compilation of astronomical works collected under the patronage of Alfonso X of Castile in the thirteenth century, which includes translations of two eleventh century Arabic texts on equatoria by Ibn al‐Samḥ and al-Zarqālī. Theorica Planetarum (c. 1261-1264) by Campanus of Novara describes the construction of an equatorium, the earliest known description in Latin Europe.