The Cedar River is a 338-mile-long (544 km) river in Minnesota and Iowa. It is a tributary of the Iowa River, which flows to the Mississippi River. The Cedar River takes its name from the red cedar (Juniperus virginiana) trees growing there. The surrounding region is known officially as the Cedar River Valley, though it is more commonly referred to simply as the Cedar Valley.

The headwaters of the Cedar River are located in Dodge County, Minnesota, consisting of a west fork and middle fork approximately three miles northeast of the town of Blooming Prairie, and an east fork approximately one mile south of the town of Hayfield. It then flows into Mower County, Minnesota through the townships of Udolpho, Lansing, Austin (where Turtle Creek and Dobbins Creek join it), and Lyle. It then flows into Mitchell County, Iowa and Floyd County, Iowa with the endpoint being located in Louisa County, Iowa at the town of Columbus Junction, where it joins with the Iowa River which then winds its way to the Mississippi River. Despite being a tributary of the Iowa River, it appears larger than the Iowa River at their confluence point. Palisades-Kepler State Park is located on the Cedar River near Cedar Rapids.

Cedar County, Iowa is named for the river.

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