Lake Biel (German: Bielersee, French Lac de Bienne) is a lake in the west of Switzerland. Together with Lake Murten and Lake Neuchâtel, it is one of the three large lakes in the Jura region of Switzerland.

The lake is 15km long and up to 4.1km wide. Its surface area is 39.3 km², the maximum depth 74m. The lake is located at 429 metres above sea level.

Lake Biel has a catchment area of about 8305 km². Water remains in the lake for an average of 58 days only. The river Aar, the river Zihl and Twanbach are the main tributaries. The river Aar was redirected into the lake in 1878.

The largest settlement along the shores of Lake Biel is the city of Biel/Bienne located on the northern end. The Sankt-Petersinsel (island) attracts tourists, mainly families. The island is located near Erlach. Jean-Jacques Rousseau lived on the island.