The main gradients in the floristic composition of European beech forests are soil carbonate content, temperature, and longitude/latitude. Although the overall species composition of beech forests is relatively uniform across Europe, several of their character species are restricted to smaller regions. The distribution ranges of these species are clustered around the glacial refugia of beech, suggesting limited migration ability rather than ecological constraints as explanatory factors. The presence or absence of these species has often been used to divide the European beech forests into geographical units. However, the syntaxonomic rank given to these units remains a matter of dispute. In most recent treatments, acidophytic and basiphytic beech forests are separated at alliance or even order level. Basiphytic beech forests can be further subdivided into meso-basiphytic beech forests, occurring in cooler climates and/or higher altitudes, and thermo-basiphytic beech forests of warmer climates and/or lower altitudes. However, most authors prefer to split the basiphytic beech forests into geographical alliances, which are then subdivided into meso- and thermo-basiphytic suballiances. In this review, a preliminary overview of the orders, alliances, suballiances, and associations of European beech forests is given. Each association name is accompanied by a short diagnosis, consisting of the geographical distribution and the position along the two main environmental gradients (soil pH and temperature). Acidophytic beech forests are classified into 23 associations within three geographical alliances. Basiphytic beech forests are grouped into 7 geographical alliances, comprising 37 thermo-basiphytic and 63 meso-basiphytic associations altogether.