Schizymenia dubyi (Chauvin ex Duby) J. Agardh is a red alga of the order Nemastomatales that is native to Europe, Asia and Oceania. The first specimen of this seaweed from the Argentinian coast was collected in the Chapadmalal intertidal wave-cut platform (38 degrees 12'S, 57 degrees 40'W) in September 2008. Taxonomic identification of the species was made on the basis of vegetative and reproductive characters and confirmed by DNA sequence analysis of the rbcL gene. The S. dubyi samples collected in the field were represented by foliose gametophytes as well as crustose tetrasporophytes. The gametophytes were distributed in patches of c. 50% coverage of the analysed quadrants (n = 20). Gametophyte abundance was 3.1 +/- 2.5 (mean +/- SD) plants per quadrant (0.04 m(2)). All these were fertile females. Molecular results placed the specimens from Argentina within the S. dubyi clade, closely related to S. dubyi from Japan and France.