Muhlenbergia microsperma is a species of grass known by the common name littleseed muhly. It is native to the Americas from the Southwestern United States and California through Central America into Peru and Venezuela. It can be found in many habitat types, including disturbed areas. It is an annual or perennial grass growing up to 60 to 80 centimeters tall. The inflorescence is an open, spreading array of thin branches bearing small spikelets which have awns up to 3 centimeters long. Spikelets lower in the inflorescence stay within sheaths and do not bloom.