蝴蝶星团（也称为M6或NGC 6405）是在天蝎座的一个疏散星团。在视觉上，他是相当接近（角距离）在银河系中心方向的人马座的梅西尔天体。

在这个星团中明亮的恒星大多是年龄在一亿年的B型蓝色恒星，但是最亮的成员却是被称为天蝎BM的橙色K型巨星。天蝎BM 是半规则变星，光度从在可见的5.5等至7.0等之间变化。在彩色的相片中，这棵橙色的星与星团中其他蓝色的星形成明显的对比。

对这个星团的距离有不同的测量结果，估计这个星团的平均距离是1,600光年，在空间中的直径大约是12光年。现代的测量显示他的总光度是4.2等。

The Butterfly Cluster (cataloged as Messier 6 or M6, and as NGC 6405) is an open cluster of stars in the constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly.

The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham, Jr. has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster (M7). Charles Messier catalogued the cluster as M6 in 1764. It was not till the 20th century that star counts, distance, and other properties were measured.