Great Globular Cluster in Hercules (also known as the Hercules Globular Cluster, Messier Object 13, Messier 13, M13, or NGC 6205) is a globular cluster in the Hercules constellation.
It was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764.

With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its real diameter is about 145 light-years, and is composed of several hundred thousand stars, the brightest of which is the variable star V11 with an apparent magnitude of 11.95. M13 is 25,100 light-years away from Earth.

Its diameter is about 23 arc minutes and is readily viewable in small telescopes. Nearby is NGC 6207, a 12th magnitude edge on galaxy that lies 28 arc minutes directly north east.