Lake Saint Clair is a lake in the U.S. state of Washington. The lake has a surface area of and reaches a depth of . It is a kettle lake with no outlet and is fed from Eaton Creek to the South.
The lake's name is a transfer from Lake St. Clair, in Michigan. The lake has four islands; two of them are named as Dollar and Goat islands.
In June 2025, swimmer's itch was reported at the lake, prompting Thurston County to issue a public advisory to avoid swimming there.