The Blackwater River is a 79.3-mile-long (127.6 km)[1] tributary of the Lamine River in west-central Missouri in the United States. Via the Lamine and Missouri rivers, it is part of the watershed of the Mississippi River.
The Blackwater River is formed by short north and south forks in Johnson County about 6 miles (10 km) northwest of Warrensburg and flows generally east-northeastwardly through Johnson, Pettis, Saline and Cooper counties, past the towns of Sweet Springs and Blackwater. It flows into the Lamine River in northwestern Cooper County, about 4 miles (6.4 km) southeast of Blackwater.
The North Fork of the Blackwater starts as one to three springs in the southwestern corner of Lafayette County near the small village of Chapel Hill, about 7 miles (11 km) south of Bates City and about 29 miles (47 km) southeast of Kansas City.
Several sections of the river's upper course have been straightened and channelized.