Lonsee is a municipality in the Alb-Donau district in Baden-Württemberg in Germany.

The population of Lonsee in 2021 is 5121;[3] the town consists of 7 villages – Ettlenschieß, Halzhausen, Lonsee, Luizhausen, Radelstetten, Sinabronn, and Urspring.

Various clubs and groups provide for an active social life.

Lonsee was first mentioned in the year 888, but the remains of a Roman fort in nearby Urspring tell of an even older history.

Lonsee has been twinned with the English town of Kingskerswell since 1989.