The Mulchatna River (Dena'ina: Vałts'atnaq') is a 160-mile (260 km) tributary of the Nushagak River in the U.S. state of Alaska. Beginning at Turquoise Lake, it flows generally southwest to meet the larger river 65 miles (105 km) northeast of Dillingham. The Mulchatna's mouth is slightly south (downstream) of the village of Koliganek on the Nushagak, which continues southwest to Nushagak Bay, an arm of Bristol Bay.