The sedge wren (Cistothorus platensis) is a small songbird of the wren family. It was formerly known as the short-billed marsh wren, and in South America is often known as the grass wren. There are about 20 different subspecies which are found across most of the Americas. Some of these forms may be separate species that could be split in the future.Adults have brown upperparts with a light brown belly and flanks and a white throat and breast. The back has pale streaks.