Messier 9 (NGC 6333) is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier in 1764.
M 9 is on the edge of a dark lane in the Milky Way, about 3° SE of the star Sabik (35 η Oph). At magnitude 7.7, this globular cluster can just be glimpsed in 10x50 binoculars under good conditions. Small telescopes show the central part of M 9; large amateur telescopes fully resolve it.
The brightest individual stars in M 9 are of apparent magnitude 13.5, making them visible in moderately sized telescopes. Nearby, about 80' to the northeast, is the dimmer globular cluster NGC 6356, and at about 80' to the southeast is the globular NGC 6342.
M 9 is one of the nearer globular clusters to the center of the Milky Way, around 5,500 light-years away from the galactic center. Its distance from Earth is about 26,000 light-years. The total luminosity of this cluster is around 120,000 times that of the Sun; its absolute magnitude is -8.04. Thirteen variable stars have been found in this cluster.