The partitioning of an area into a number of homogeneous regions based on ecological criterions is called ecoregionalization. The resulting districts are denoted as ecoregions. Regionalization is one specific kind of classification procedures that has special characteristics and considers the spatial aspect of the regions. Classification techniques will be compared to regionalization methods and regionalization procedures are compared among themselves. The workflow as well as the advantages and disadvantages of each method are described in detail. Graph theory is an essential background for the performance of those regionalization techniques since the regions are represented as vertices which are connected by edges. Furthermore, a minimum spanning tree is created during the regionalization process in order to connect only those regions that are very similar. The quality and the performance of each method and the results are analyzed. The book concludes with a summary and provides ideas for further developments in the outlook.