Non-native tree species (NNT) have been used in European forestry already for several centuries. The share of NNT in the forest cover, their economic importance and the perceived ecological risk, however, largely varies across Europe. In addition, countries respond with their national policies and legislation differently to supernational frameworks like European Union directives or international treaties and conventions on forestry and nature conservation. This results in diverse policy approaches and a wide range of regulatory intensities concerning NNT.