The Spring River is a 57-mile (92 km) long river which flows through the U.S. states of Missouri and Arkansas. It consists of two branches, the South Fork of the Spring River and the Spring River proper. The South Fork of the Spring River starts in Howell County, Missouri and flows south through Fulton and Sharp counties in Arkansas. The South Fork of the Spring River joins the Spring River proper near the town of Hardy, Arkansas. The South Fork is a quiet stream with gravel bars that are ideal for camping.
The Spring River proper begins where Mammoth Spring and Warm Fork of the Spring River merge at Mammoth Spring State Park in Mammoth Spring, Arkansas. Mammoth Spring is the outlet of an underground river that runs from Missouri into Arkansas. Over 9.78 million US gallons (37,000 m3) per hour flow out of the massive spring and forms the Spring River. Being predominantly spring fed with water averaging 58 °F (14 °C), the river is kept cool during warmer months and is suitable trout habitat for several miles.