The Susitna River /suːˈsɪtnə/ (Sasut Na’ in Ahtna or Susitnu in Dena'ina) is a 313-mile (504 km) long river in the Southcentral Alaska. It is the 15th largest river in the United States, ranked by average discharge volume at its mouth. The river stretches from the Susitna Glacier to Cook Inlet's Knik Arm.