A minor planet is an astronomical object in direct orbit around the Sun that is neither a dominant planet nor originally classified as a comet. Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects. The first minor planet discovered was Ceres in 1801 (although from the time of its discovery until 1851 it was considered to be a true planet). The orbits of more than 570,000 objects have been archived at the Minor Planet Center.

The term "minor planet" has been used since the 19th century to describe these objects. The term planetoid has also been used, especially for larger objects. Historically, the terms asteroid, minor planet, and planetoid have been more or less synonymous, but the issue has been complicated by the discovery of numerous minor planets beyond the orbit of Jupiter and especially Neptune that are not universally considered asteroids. Minor planets seen outgassing may receive a dual classification as a comet.