Comparison of the twenty most frequently used petrogenetic classifications of granitoids is summarized using petrography, nature and abundance of enclaves, mineralogy, major and trace element, and isotope geochemistry. This comparison indicates considerable agreement between most authors concerning the main divisions. Differences result either from different genetic models or from the weighting of the criteria used, such as nature of the source, relative proportions of crustal and mantle contributions, magmatic processes, and types of emplacement. In the classification proposed here, three main groups of granitoids correspond respectively to a crustal, a mantle, or a mixed (crustal and mantle) origin of the magmas. Each of these main groups is subdivided into two or three types. Distinct petrographic, mineralogical, and chemical characteristics result from differences in the origin and tectonic setting of the granitoid magmas. Consequently, granitoids with well-defined petrographic, mineralogical, chemical features and ages may provide information on the changes of tectonic settings with space, time, or both, i.e. they may be used as geotectonic tracers.