The Lac de Guiers is a large freshwater lake in northern Senegal, south of the city of Richard-Toll. It is a chief source of fresh water for the city of Dakar, hundreds of kilometers to the southeast, through underground pipes.

It is about 35 kilometers long and 8 kilometers wide, and is supplied by the Bounoum River that flows north into its southern end, from Fouta. Water used to flow out to the Senegal River north through the Portuguese River, but this has been replaced by a straight canal to Richard-Toll. The shores are mostly fertile. The north shore and surrouding area have been converted to a large irrigated sugar-growing region, with water from this lake.

The lake has a complicated history involving the kingdoms of Tekrur and Waalo and the Empire of Jolof (Diolof). Notably, the settlement of Nder, the third and final capital of the former Kingdom of Waalo, was located on the west shores of the Lake. The royal compound or "keur" is still there. Previously Lac de Guiers was called Lac du Panier Foule or Pania Fuli, referring to the Peulh people.