Oyster reefs are among the most species-rich but at the same time among the most endangered marine habitats in the world. Once, huge areas of three-dimensional biogenic structures formed by the native European oyster (Ostrea edulis) provided a hard substrate on the seabed of the German North Sea, thus providing valuable ecosystem services and habitat for numerous species. Today, O. edulis and its biocoenoses are classified as functionally extinct in the German Bight. The successful and long-term reintroduction of this important ecological key species is currently being investigated and promoted by two projects of the German Federal Agency for Nature Conservation. The return of the European oyster to its former habitat, for which the exclusion of any bottom-contacting human interference is a general prerequisite, could lead to a significant increase in biodiversity. The initial results of the two projects provide an important basis for developing and implementing a large-scale German restoration programme to reinstall a healthy population of the native oyster and its valuable ecosystem services.