Lygnern () is a lake in the municipalities of Kungsbacka and Mark, western Sweden. With an area of 33 kmò, it is the largest lake in Halland County. Its main outflow is RolfsÃÂ¥n, which in turn empties out into the Kungsbacka Fjord.
The lake serves as a source of drinking water for Kungsbacka. In 2006, it was nominated as the cleanest lake in Sweden, as 98% of the surveyed residents of the municipality were satisfied with the water quality.
Ten fish species have been found in the lake, which is particularly rich in pike, trout and European perch.