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Abstract Members of the genusChondrusare well-known from temperate and cold waters.Chondrus ocellatusHolmes was reported from Hawai‘i Island (19° N latitude) in 1999 as a new record based on vegetative and tetrasporangial characteristics. The first specimens were collected by Setchell in 1900 in Hilo, HI. The presence of aChondrusspecies in the subtropics has been a phycological enigma for over 100 years. We addressed the question of species identity and biogeographic affinities of the HawaiianChondruswith fresh cystocarpic material, DNA samples, and phylogenetic analyses. Analysis and comparison of five genes (nuclear: EF2; plastid:psbA,rbcL, and 23S/UPA; mitochondrial: COI) from HawaiianChondrusand holotype and topotype material of 10 of the 11 acceptedChondrusspecies indicate that Hawaiian specimens areC. retortusMatsumotoetShimada. However, unlike type material, the Hawaiian specimens are commonly pinnulate, vary significantly in secondary medullary filament density, and have mature cystocarps filling the entire medullary space. This study shows the value of using multi-gene loci and comparing multiple sequences of several species to confirm taxonomic conclusions. Our findings suggest thatC. retortusmay have immigrated via rafting on natural floating material or on ships’ hulls. Solving this old puzzle adds new insight into Hawaiian phytogeography.