Allens Creek Reservoir is a planned water storage lake permitted for construction on Allens Creek, a tributary of the Brazos River, in Austin County. The permit to build the lake was originally issued to Houston Lighting and Power (Reliant Energy) in 1974 by the Texas Natural Resource Conservation Commission, now known as the Texas Commission on Environmental Quality (TCEQ).

The reservoir was originally to have served as a cooling lake for a nuclear power plant. When Reliant Energy abandoned plans to construct the nuclear power plant at the Allens Creek site in the 1980s, the property was purchased by the City of Houston and the Brazos River Authority with the purpose of building a water storage reservoir.

The new reservoir will provide water to meet the future needs of the City of Houston and surrounding communities. When complete, the reservoir will supply 92,000 acre-feet of water supply and access to water recreation for the area. Swimming, boating, fishing and camping facilities will be available to the general public. Construction is expected to begin by 2018.