Tustumena Lake (Dena'ina: Dusdu Bena) is a lake on the west side of the Kenai Peninsula in southcentral Alaska, within Kenai National Wildlife Refuge and near the town of Kasilof.

With a maximum depth of 950 feet (290 m), Tustumena Lake is exceptionally deep; it is deeper than Cook Inlet.

The lake and the area around it are known for game hunting, and for the Tustumena 200 Sled Dog Race.

This lake has a reputation for being very dangerous to small boats due to the high winds that regularly blow off of Tustumena Glacier.

Early trophy hunters from the 1890s and later took world record moose from the north shore, and the first hunting guide to obtain a license to guide hunters in the State of Alaska called this area home.