The vegetative and reproductive morphology and anatomy of Halymenia specimens from the Philippines were studied and four species recognised: H. dilatata Zanardini, H. durvillei Bory de Saint-Vincent, H. maculata J. Agardh and H. porphyraeformis Parkinson. As many Halymenia taxa have previously been reported from the western Pacific and Malayan region, specimens from neighbouring regions and type material of the most relevant taxa were compared with the collections from the Philippines. From these studies, H. ceylanica Harvey ex K Kutzing H. durvillei var. denudata Weber-van Bosse, H. durvillei var. edentata Weber-van Bosse, H. formosa Harvey ex Kutzing, H. microcarpa (Montagne) P. Silva and H. venusta Borgesen are considered to be synonyms of H. durvillei. H. porphyraeformis is reported from the region for the first time, but was found in earlier collections identified as the superficially similar H. dilatata.