Cyperus flavescens, commonly known as the yellow flatsedge, is a species of flowering plant belonging to the family Cyperaceae.
Cyperus flavescens was first described by the Swedish botanist Carl Linnaeus in 1753. Linnaeus based his on specimens collected in marshes in Germany, Switzerland, and France ("habitat in Germaniae, Helvetiae, Galliae paludosis").
Cyperus flavescens has a cosmopolitan distribution. It is native to North America, South America, Europe, Asia, and Africa. It was introduced to New South Wales and Queensland in Australia. In North America (north of Mexico), it is most common in the eastern United States.