The headwaters of the Lampasas River are in western Hamilton County 16 miles west of Hamilton. It flows southeast for about 75 miles and runs through Lampasas County, Burnet County and Bell County. In Bell County, the Lampasas turns northeast and is dammed five miles southeast of Belton to form Stillhouse Hollow Lake. The river continues for nine miles past Stillhouse Hollow to the confluence with the Leon River, where the two rivers form the Little River near the town of Little River, Texas. Tributaries to the Lampasas include Bennett, Lucy, Sulpher, Simms, School, and Turkey creeks.