Tallassee is a city on the Tallapoosa River, located in both Elmore and Tallapoosa counties in the U.S. state of Alabama. At the 2020 census, the population was 4,763. It is home to a major hydroelectric power plant at Thurlow Dam operated by Alabama Power Company.

The Tallapoosa River runs 265 miles (426 km) from the southern end of the Appalachian Mountains in Georgia, United States, southward and westward into the Appalachian foothills in Alabama. It is formed by the confluence of McClendon Creek and Mud Creek in Paulding County, Georgia. Lake Martin at Dadeville, Alabama is a large and popular water recreation area formed by a dam on the river. The Tallapoosa joins the Coosa River about 10 miles (16 km) northeast of Montgomery near Wetumpka to form the Alabama River.