Alopecurus geniculatus is a species of grass known by the common name water foxtail or Marsh foxtail.
It is native to much of Eurasia and North America, where it grows in moist areas. This is a perennial grass forming bunches of erect stems up to about 60 centimeters in maximum height. The leaves are 8 to 12 centimeters in maximum length. The inflorescence is a dense panicle up to 6 or 7 centimeters long which blooms in dusty yellow-orange anthers.