Lake Biel or Lake Bienne (German: Bielersee; French: Lac de Bienne [lak də bjɛn]) is a lake in western Switzerland . Together with Lake Morat and Lake Neuchâtel , it is one of the three large lakes in the Jura region of Switzerland. It lies on the language boundary between German and French speaking areas.

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