乱子草属（学名：Muhlenbergia）是禾本科下的一个属，为多年生草本植物。该属共有约100种，分布于北美、喜马拉雅至日本。

Muhlenbergia is a genus of plants in the grass family.

The genus is named in honor of the German-American amateur botanist Gotthilf Heinrich Ernst Muhlenberg (1753-1815). Many of the species are known by the common name muhly. The greatest number are native to the southwestern United States and Mexico, but there are also native species in Canada, Central and South America and in Asia.