A novel, Gram-staining-positive, facultatively anaerobic, non-motile and coccus-shaped bacterium, strain WL80(T), was isolated from the gut of an abalone, Haliotis discus hannai, collected from the northern coast of Jeju in Korea. Optimal growth occurred at 30 °C, pH 7-8 and with 1% (w/v) NaCl. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that strain WL80(T) fell within the cluster of the genus Actinomyces, with highest sequence similarity to the type strains of Actinomyces radicidentis (98.8% similarity) and Actinomyces urogenitalis (97.0% similarity). The major cellular fatty acids were C18 : 1ω9c and C16 : 0. Menaquinone-10 (H4) was the major respiratory quinone. The genomic DNA G+C content of the isolate was 70.4 mol%. DNA-DNA hybridization values with closely related strains indicated less than 7.6% genomic relatedness. The results of physiological, biochemical, chemotaxonomic and genotypic analyses indicated that strain WL80(T) represents a novel species of the genus Actinomyces, for which the name Actinomyces haliotis sp. nov. is proposed. The type strain is WL80(T) ( = KACC 17211(T) = JCM 18848(T)).