A survey of marine benthic community biodiversity off Low Island (Southern Ocean) was carried out by the Spanish Antarctic Expedition Bentart 2006, using the BIO Hespérides. Samples from the expedition included an important collection of hydroids. A total of 39 species was recorded, two of them being new to science (Eudendrium bentart sp. nov., and Orthopyxis curiosa sp. nov.), belonging to the subclasses Anthoathecata and Leptothecata. Anthoathecates are represented by only two species, both referable to the genus Eudendrium. The 37 leptothecate species belong to the families Campanulinidae, Lafoeidae, Haleciidae, Schizotrichidae, Kirchenpaueriidae, Sertulariidae and Campanulariidae. Sertulariidae is the most diverse family with 16 species (41%), followed by Campanulariidae with five species (13%) and Haleciidae, Schizotrichidae and Kirchenpaueriidae with four species (10%) each. At the generic level, the predominant genera are Symplectoscyphus with nine species (23%) and Halecium, Oswaldella and Schizotricha with four species (10%) each. Fifteen of the 39 species represent new records for the waters surrounding Low Island, as also are three (Lafoeina, Opercularella and Orthopyxis) of the 16 genera. In all, 33 species (c. 81%) are endemic to Antarctic waters, either with a circum-Antarctic (20 species, c. 49%) or West Antarctic (13 species, c. 32%) distribution. Thirty-eight species (c. 93%) are restricted to Antarctic or Antarctic/sub-Antarctic waters; only three species have a wider distribution. The Low Island hydroid fauna is composed of typical representatives of the Antarctic benthic hydroid fauna, with good representation of some of the most diverse and widespread Antarctic genera such as Antarctoscyphus, Oswaldella, Schizotricha and Staurotheca.