Muhlenbergia filiformis, known by the common name Pullup muhly, is a species of grass. It is native to western North America from western Canada through the Western United States to northern Mexico. Pullup muhly grows in many types of moist to wet habitats. Muhlenbergia filiformis is an annual herb producing clumps of decumbent stems up to 30 centimeters long which root where their nodes touch the substrate. The inflorescence is a narrow, cylindrical array of appressed branches bearing many spikelets each about a millimeter long.