Charles Messier (1730 – 1817) was the French astronomer and comet hunter most known for publishing an astronomical catalog consisting of deep sky objects visible only in the Northern hemisphere that originally included 45 objects, and today are known as the 110 "Messier objects". The Messier catalog contains notable examples of every known type of deep sky object, including galaxies, planetary nebulae, open clusters, and globular clusters. The objects' famous designations, from M1 to M110, are still in use by professional and amateur astronomers.

The purpose of the catalog was to help astronomical observers to distinguish between permanent objects in the sky and transient objects such as comets. While the full NGC catalog (New General Catalog) lists thousands of similar objects, the Messier catalog only represents some of the brighter deep sky objects detectable at the time that hindered Messier's comet search. Since Messier lived and worked in the Northern hemisphere, over 100 similar notable objects visable only in the Southern hemisphere such as the Cat's Eye Nebula, and the Greater and Lesser Magellanic Clouds are not included in his catalog.