Ten strains of an unknown Campylobacter species were isolated from the livers of spotty liver disease affected birds in Australia. They are Gram negative, microaerobic, catalase and oxidase positive and urease negative. Unlike most other species of the genus Campylobacter, most of the tested strains of this novel species hydrolyse hippurate and half of them could not reduce nitrate. All strains showed resistance, or intermediate resistance, to nalidixic acid and most of them were resistant to cephalothin. Examination of negatively stained cells under transmission electron microscopy revealed that they were S-shaped, with bipolar unsheathed flagella. Phylogenetic analyses based on the 16S rRNA gene and the heat shock protein 60 (hsp60) gene sequences indicated that the strains formed a robust clade that was clearly distinct from recognised Campylobacter species. Unusually, they have a mol% G+C of 27.9 %; lower than any previously described Campylobacter species and have less than 84% average nucleotide identity to the nearest sequenced species. Taken together, these data indicate that the strains belong to a novel Campylobacter species for which the name Campylobacter hepaticus sp. nov. is proposed, with the type strain NCTC 13823T (=CIP111092T).