Messier 23 (also known as NGC 6494) is an open cluster in the constellation Sagittarius. It was discovered by Charles Messier on June 20, 1764.

M23 is at a distance of about 2,150 light-years away from Earth, its radius is around 15-20 light years. There are some 150 identified members in this cluster, the brightest being of magnitude 9.2. M23 can be found with a modestly sized telescope in the rich starfields of the Sagittarius Milky Way.