All maps of vegetation or habitats are based on a system of classification. For vegetation, this has usually been based on phytosociological synsystems, while classifications of habitats, being more recent, have been produced at national, regional and international levels (e.g. Czech biotopes, Nordic vegetation types and Corine biotopes). This chapter discusses the classification systems in use for mapping vegetation and habitats in different countries, and also the work towards harmonisation at European scale. It introduces the EUNIS habitat classification, proposed as a European standard under the EU INSPIRE Directive (Directive 2007/2/EC), and its crosswalks to and from other typologies. Finally, it presents the habitat typologies used for monitoring, statistical and distribution modelling approaches as developed by the BioHab and EBONE projects.