Lonsee is a municipality located in the Alb-Donau district within the German state of Baden-Württemberg. As of 2021, the town has a population of 5,121 residents and is composed of seven distinct villages: Ettlenschieß, Halzhausen, Lonsee, Luizhausen, Radelstetten, Sinabronn, and Urspring.
The municipality features essential infrastructure including a town hall, two schools, and two railway stations situated on the Fils Valley Railway. The area is known for an active social life supported by various clubs and groups. Historically, Lonsee was first mentioned in 888, though archaeological remains of a Roman fort in nearby Urspring indicate an older history. Since 1989, the town has maintained a twinning relationship with Kingskerswell, England.