1. One of a set of five positions at which a small object can maintain a stable orbit under the influence of two more massive objects.
2. A point in space at which a small body, under the gravitational influence of two large ones, will remain approximately at rest relative to them.

The existence of such points was deduced by the French mathematician and astronomer Joseph-Louis Lagrange in 1772.

In 1906, the first examples were discovered. These were minor planets moving in Jupiter’s orbit, under the influence of Jupiter and the sun.