The Sedge Wren, Cistothorus platensis, is a small songbird of the Wren family. It is also known as the Short-billed Marsh Wren and in South America 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.

Adults have brown upperparts with a light brown belly and flanks and a white throat and breast. The back has pale streaks. They have a dark cap with pale streaks, a faint line over the eye and a short thin bill.

Their breeding habitat is wet meadows and marsh edges in eastern North America and central Canada. The nest is a round lump attached to low vegetation, entered from the side; it is usually well-hidden. The male often builds several unused nests in his territory; he may puncture the eggs of other birds nesting nearby.

These birds migrate to coastal areas in the southeastern United States, and the entire Gulf Coast southe through eastern Mexico.

These birds forage low in vegetation, sometimes flying up to catch insects in flight. They mainly eat insects, also spiders.

The male's song is a rattling trill.

This bird's numbers are declining, possibly due to loss of habitat.