Iliamna Lake, Freshwater lake in Lake and Peninsula Borough, Alaska

Iliamna Lake is a freshwater lake in southwest Alaska, at the base of the Alaska Peninsula. It is 77 miles (124 km) long and up to 22 miles (35 km) wide, with a maximum depth of 988 feet (301 m) at its eastern end. That eastern end is broken by numerous small islands, while the western end is broad, shallower and nearly island-free. The villages of Iliamna, Newhalen, Kokhanok, Pedro Bay, Pope-Vannoy Landing and Igiugig lie on its shores.

The lake appears as 'Oz[ero] Bol[shoy] Ilyamna' (Big Ilyamna Lake) on Chart 1455 of the Russian Hydrographical Department, published in 1852. An earlier Russian map of 1802 named it 'Oz[ero] Shelekhovo' after explorer Grigory Shelekhov. The Dena'ina name Nila Vena, "island's lake", is the source of the name Iliamna.

The Dena'ina Athabascan people called this lake Nila Vena, meaning island's lake, showing how central it was to their way of life. This name still reflects the deep ties that local communities have to the water today.

The lake is ice-covered from December to May, so open-water access and fishing concentrate in the warmer months. The villages of Iliamna, Newhalen, Kokhanok, Pedro Bay, Pope-Vannoy Landing and Igiugig lie on the shore. The one-lane Williamsport-Pile Bay Road, 15.5 miles long with four bridges, is a gravel utility road for hauling boats and freight, not for general traffic.

Local stories speak of a giant blackfish living in the lake's depths, which inspired a newspaper to offer a substantial reward for proof of its existence back in the 1970s. This tale has fueled visitors' curiosity about what might lurk beneath the water.