The important genus Agathis is well represented in the rich flora of the island of Borneo. In some places it forms nearly pure stands and has been heavily exploited for its resin and for lumber. Three species, one of which merely represents leaf variations from another, have been proposed previously for this genus in Borneo (Warburg, 1900; Meijer Drees, 1940). Several hundred collection numbers can be found in the major herbaria, much the majority of which belong to one species. This is particularly true for the non-Asian herbaria. During several field trips to Borneo, however, I identified three additional quite distinct unnamed species. The great variability of leaf size and shape even on individual plants in this genus together with difficulty in making good representative collections from these immense trees has surely hindered the recognition of the distinctions to be described here. None of these species has been totally overlooked, to be sure, inasmuch as a few specimens of each have previously reached the major herbaria. Furthermore, Whitmore (1979) concluded after seeing some of this material that it did not correspond to any of the species already described from Borneo but in fact represented Agathis dammara, a species not actually found in Borneo. I will describe all five Borneo species in order to clarify their distinctions. Only fully mature pollen cones and seed cone scales will be considered in this description along with as much as possible the normal foliage leaves as opposed to the poorly developed leaves of primary branches and seed cone bearing shoots.