In the present study we report on a survey of the diversity of Halymeniales (Rhodophyta) collected during two expeditions along the coasts of southern Madagascar and Guadeloupe. The aim of these marine expeditions was to overcome the lack of knowledge on the algae and more generally on the diversity of benthic organisms by means of a modern systematic approach. Among the collected material, specimens morphologically identified as halymeniacean taxa have been sequenced for the DNA barcode gene (COI-5P). Subsequently, those recognized as putative new taxa were thoroughly observed to document their vegetative and reproductive anatomical struc- tures. Phylogenetic analyses inferred from additional genetic markers (rbcL, LSU) were also conducted to assess the phylogenetic relationships of the Malagasy and Guadeloupian samples with their worldwide relatives. The first published result was a report of two novel species of the genus Yonagunia from Madagascar (Manghisi et al. 2015), moreover additional new halymeniacean taxa were uncovered and will be formally described.