Alagnak River, AK

The Alagnak River is a 79 mile (127 km) long river in Alaska. It has a catchment area of approximately 1400 square mi (3600 km²). It is located in central Lake and Peninsula Borough. In Yupik, the word "Alagnak" means "to err." Every year, the river changes its course and branches anew, for which reason it is sometimes called the "Branch River."

It begins as the outflow of Kukaklek Lake in Katmai National Park and Preserve and meets the sea at Bristol Bay. The beginning of the river lies in the Aleutian Range. The first six miles of the river run slowly through the tundra. Vegetation along the upper part of the river consists mostly of spruce. Afterwards, the valley becomes much narrower with near-vertical rock faces. Miles 7-14 run through a narrow canyon at around 7.5 mph. The Nonvianuk River runs into the Alagnak at around mile 20. To the west, the river meanders over the Alaska Peninsula before flowing into the Kvichak River, which itself flows into Bristol Bay.

The upper 67 mi (108 km) of the river is designated as a protected "wild and scenic river" in accordance with ANILCA, the Alaska National Interest Land Conservation Act. This part of the river is known as the Alagnak Wild River.

The Alagnak is one of the most important rivers for sport fishing in Alaska. In the water, there are several varieties of salmon, including sockeye salmon, pink salmon, chum salmon, king salmon, and silver salmon. There are also rainbow trout, char, arctic grayling, and northern pike.