Lake Austin is a reservoir on the Colorado River in Austin, Texas in the United States. The reservoir was formed in 1939 by the construction of Tom Miller Dam by the Lower Colorado River Authority. Lake Austin is one of the seven Highland Lakes created by the Lower Colorado River Authority, and is used for flood control, electrical power generation, and recreation. Loop 360 spans the lake at the Pennybacker Bridge.

The other reservoirs on the Colorado River are Lake Buchanan, Inks Lake, Lake LBJ, Lake Marble Falls, Lake Travis, and Lady Bird Lake.