Glass sponges represent a dominant group of megabenthic deep-sea fauna and play a key role in benthic deep-sea ecosystems. Especially in the Clar- ion-Clipperton Fracture Zone (CCFZ), a potential deep-sea mining area, they grow on polymetallic nodules or on the surrounding sediment. We investi- gate hexactinellids from the CCFZ to understand the ecological aspects of deep-sea mining and support the development of future pre-mining risk assessments and monitoring actions. Therefore, this study is published as part of a series of studies, all focusing on deep-sea glass sponges from the CCFZ. Resolving genetic relationships between species is still a funda- mental as well as challenging task. Especially under- studied groups mostly lack resolution. Combining results derived from taxonomic and phylogenetic data gives deeper insights into glass sponge relationships. Here, we present (1) a set of new primers for sequencing mitochondrial 16S rDNA as well as nuclear 18S and 28S rDNA of glass sponges, (2) first DNA sequencing data for 6 hexactinellid genera and 19 species, as well as (3) the most comprehensive phylogenetic tree of hexactinellid sponges to date including data available from previous studies.