A description of the defining characteristics of Gardenia (Rubiaceae) and a revision of the Philippine species distinguished mainly by calyx morphology are presented. A key to five species of Gardenia recognised for the Philippines, full descriptions and illustrations, and a list of names which should be excluded from Gardenia are given. Relevant Philippine names for which holotypes were not indicated or have been destroyed are lectotypified. Two new endemic species, Gardenia ornata K.M.Wong and G. vulcanica K.M.Wong, are described. Gardenia elata Ridl. and G. mutabilis Reinw. ex Blume are newly applied to Philippine species previously enumerated under other names. Gardenia pseudopsidium (Blanco) Fern.-Vill. is considered a doubtful name, to which some authors have referred the endemic G. barnesii Merr.

Two new species of Gardenia (Rubiaceae), Gardenia beamanii Y.W.Low and Gardenia chanii Y.W.Low, endemic to Borneo, are described. These species are distinguished from Gardenia griffithii Hook.f. and Gardenia pterocalyx Valeton, respectively, to which they are superficially similar in calyx characters. Gardenia pterocalyx is lectotypified.