NGC 6540 is a globular cluster of stars in the souther constellation Sagittarius, positioned about 4.66° away from the Galactic Center.

[5] It was discovered by German-British astronomer Wilhelm Herschel on May 24, 1784, with an 18.7-inch mirror telescope, who described the cluster as "pretty faint, not large, crookedly extended, easily resolvable".

It has an apparent visual magnitude of 9.3[3] with an angular diameter of about 9.5 arcminutes.

It was originally thought to be an open cluster before being designated a globular.

[1] The cluster includes a peculiar X-ray source of uncertain type.