A bacterium, designated strain lac18(T), was isolated in pure culture from the mucosal jejunum of a healthy pig, using a medium selective for anaerobic lactic acid bacteria and containing porcine gastric mucin as the main carbon and nitrogen source. Cells of this strain were coccus-shaped, arranged singly or in pairs and were Gram-stain-negative, oxidase-negative, non-spore-forming, anaerobic and microaerotolerant. An analysis based on 16S rRNA gene sequences indicated that strain lac18(T) should be assigned to the genus Veillonella, class Clostridia, phylum Firmicutes. 16S rRNA and dnaK gene sequence-based phylogenetic analyses both indicated that the most closely related species were Veillonella ratti ATCC 17746(T) (similarities of 96.6 and 84.5 %, respectively) and Veillonella criceti ATCC 17747(T) (similarities of 96.6 and 83.4 %, respectively). The results of DNA-DNA hybridizations between strain lac18(T) and these Veillonella species and the type species of the genus, Veillonella parvula DSM 2008(T), confirmed the genotypic distinctness of the novel isolate. Data from phenotypic studies also served to differentiate strain lac18(T) from related strains. Therefore strain lac18(T) represents a novel species of the genus Veillonella, for which the name Veillonella magna sp. nov. is proposed. The type strain is lac18(T) (=CCUG 55454(T)=CIP 109767(T)=DSM 19857(T)=JCM 15053(T)).