Marienwerder (German pronunciation: [maˌʁiːənˈvɛʁdɐ] ⓘ) is a municipality in the district of Barnim in the state of Brandenburg, Germany.

Every summer since 2004, a two-day music festival called Inselleuchten takes place in Marienwerder in mid-July.

From 2007 on the popular actor and musician Axel Prahl hosted it as presenter and figurehead.

In 2016 Suzanne Vega gave a stage show here.

Due to the COVID-19 pandemic the 2020 festival was canceled and rescheduled to 2021.