Lac Brenet (French pronunciation: [lak bʁənɛ]) is a lake in the Vallée de Joux, canton of Vaud, Switzerland.

It is located north of the Lac de Joux, only 200 metres away.

The lake used to drain naturally underground and the water resurfaced at the source of the Orbe River.

Today the lake is used as a reservoir of the hydroelectric plant at Vallorbe.

This article related to a lake in Vaud is a stub.