The Coldwater River is a 19.4-mile-long (31.2 km) stream in the U.S. state of Michigan. Located in western Michigan, the river is a part of the Grand River drainage basin. The Coldwater River flows through Barry and Kent counties, and the drainage basin also includes a large portion of southwest Ionia County and a tiny portion of Sunfield Township in the northwest corner of Eaton County. Major tributaries (from the mouth):