The Sac River is a river in southwest Missouri. It is 118 miles (190 km) long, with headwaters in Lawrence and Greene counties; the headwaters join near Greenfield, then flow north through the Ozarks, to the Osage River, ending just above Osceola in Truman Reservoir.
The Big Eddy Site, an archaeological dig, is along the Sac River within Cedar County. Eleven feet of river sediment at the site provides a stratigraphy that suggests more than 10,000 years of nearly constant occupation by American Indians, potentially pre-dating the Clovis culture and contributing to the knowledge of the Dalton and San Patrice cultures.
- Confluence with the Osage River in an arm of the Harry S. Truman Reservoir in St. Clair County, Missouri: 
- Greene County, Missouri: 
- Watershed Assessment and map of the Sac River basin, from a Missouri Department of Conservation website[dead link]
- Stockton Lake map showing the Sac River, from an Army Corps of Engineers website[dead link]
- Unearthing the mysteries of man, from the website of the Association of Missouri Electric Cooperatives[dead link]
- The Big Eddy Site, from the Center for Archeological Research at Missouri State University