Below are the definitions used to assign R1b-U106/S21+ Research Group participants to geographic regions for grouping purposes. These definitions are based on an approximate geographic division of mainland Europe on a grid system with north west, south west, south east, north east and central divisions.

Cultural and historical political divisions are not considered since there has been no consistent division of Europe over the time frame being considered for U106/S21 study, i.e. 1000s of years. Country names are used here only as a point of reference for convenience and may not correspond to past or future United Nations-recognized independent states.