Hilda asteroids are asteroids with a semi-major axis between 3.7 AU and 4.2 AU, an eccentricity greater than 0.07, and an inclination less than 20°. They do not form a true asteroid family, in the sense that they do not descend from a common parent object. Rather, these asteroids are in a 2:3 orbital resonance with Jupiter. Hildas move in their orbits so that their aphelia put them opposite Jupiter, or 60 degrees ahead of or behind Jupiter at the L4 and L5 Lagrangian points. Over three successive orbits each Hilda asteroid passes through all of these three points.
The namesake is 153 Hilda, discovered by Johann Palisa in 1875.
