Sponges are one of the most representative and abundant benthic groups, with records from different environments and depths. Regarding their diversity, around 450 marine species are described in the Brazilian Exclusive Economic Zone (EZZ), with only 17 of them belonging to the class Hexactinellida. These sponges are found in cold and deep waters and remain poorly studied due to the high costs and logistical challenges of sampling. This study aims to describe hexactinellid species of the family Hyalonematidae, sampled in the Southwestern Atlantic (Campos Basin, off Rio de Janeiro state), and deposited at the Museu Nacional (MNRJ-UFRJ), in Rio de Janeiro, Brazil. The three specimens analyzed here belong to Hyalonema. This genus encompasses 100 species described worldwide, which are classified in 12 subgenera. In Brazil, four species have been recorded to date: H. (Coscinonema) schmidti, H. (Cyliconema) conqueror, H. (Cyliconemaoida) alucia, and H. (Prionema) dufresnei. Among the specimens examined, two potentially new species are being described, one H. (Corynonema) sp. and one H. (Cyliconema) sp. Notably, the former represents the first record of this subgenus in the Atlantic Ocean. Hyalonema (Cyliconema) sp. is characterized by acanthophorae in its basalia, pinnular pentactines in the dermalia and atrialia, diactins, hexactins, and pentactins in the choanosome, as well as amphidisc microscleres (macro-, meso-, and microamphidiscs). In turn, H. (Corynonema) sp., presents basalia with acanthophorae, pinnular pentactins and hexactins in its dermalia and atrialia, diactins, pentactins and hexactins in the choanosome, together with amphidisc microscleres (macro-, meso- and microamphidiscs) and microhexactins. The uniqueness of the samples, the potential discovery of new species, and the first Atlantic record of the subgenus highlight the need for further taxonomic studies on the group, which appears to be markedly understudied in the SW Atlantic.