An order of flowering plants (angiosperms) in the euasterid I group of the asterid eudicotyledons. The order consists of five families and approximately 17,500 species. The circumscription of Gentianales has been widened to include Rubiaceae, largely on the basis of deoxyribonucleic acid (DNA) sequence data. Circumscription of Loganiaceae has also changed on the basis of these data, with many taxa, including the ornamental Buddleja, being transferred to Lamiales. The order is characterized by opposite leaves, frequent occurrence of alkaloids, and the presence of internal phloem in the wood (not in Rubiaceae).