In this first monography of the genusCorsiatwo new sections are distinguished, viz.Sessilisvan Royen with sessile labellum in the flower andUnguiculatisvan Royen with a clawed labellum. In these two sections 6 and 17 species respectively are described. In theSessilissection3new species are described,C. cornuta, C. triceratopsandC. virido-purpurea, while in theUnguiculatissection 11 new species are described,C. cyclopensis, C. papuana, C. haianjensis, C. pyramidata, C. brassii, C. wubungu, C. resiensis, C. clypeata, C. boridiensis, C. huonensis and C. merimantaensis.Preceding the descriptions of the species an introduction dealing with morphology, ecology and taxonomy is given, while with each description details about ecology etc. is included.