French astronomer who was the first to compile a systematic catalog of nebulae (nebula) and star clusters. In Messier's (Messier catalog) time a nebula was a term used to denote any blurry celestial light source.

In 1751 Messier became a draftsman and recorder of astronomical observations for the noted French astronomer Joseph-Nicolas Delisle. Messier was the first in France to observe the anticipated return of Halley's Comet in 1758–59, and from that time he became an ardent searcher for new comets. Called the comet ferret by King Louis XV, Messier independently discovered 13 of them and observed many more.

In 1760 he began compiling a list of nebulae so that he could distinguish better between nebulae and comets, which look alike when viewed with a small telescope such as was available to Messier. Many of these nebulae, including some of the most prominent, are still known by his catalog numbers. Messier was elected a foreign member of the Royal Society of London in 1764 and obtained a seat in the Paris Academy of Sciences in 1770.