The Gentianaceae is an angiosperm family in the order Gentianales consisting of 102 genera and approximately 1750 species, distributed in all areas of the world, except Antarctica. Most species are in temperate areas, but the gentians belonging to the most ancestral evolutionary branches are from the Neotropics. Gentians can be small herbs without chlorophyll to tall rainforest trees, but most are annual or perennial herbaceous plants. This worldwide treatment includes detailed information on vegetative and reproductive morphology, flower and wood anatomy, embryology and cytology, infrafamilial classification and phylogenetic relationships, as well as ethnobotanical uses and conservation for all genera. Keys to the seven tribes and genera are provided, and the morphology and distribution of each genus is described. The tribe Voyrieae is here included in the family classification, giving a total of 7 tribes in Gentianaceae.