AbstractKlebsiella oxytocacauses opportunistic human infections and post-antibiotic haemorrhagic diarrhoea. ThisEnterobacteriaceaespecies is genetically heterogeneous and is currently subdivided into seven phylogroups (Ko1 to Ko4, Ko6 to Ko8). Here we investigated the taxonomic status of phylogroups Ko3 and Ko4. Genomic sequence-based phylogenetic analyses demonstrate that Ko3 and Ko4 formed well-defined sequence clusters related to, but distinct from,Klebsiella michiganensis(Ko1),Klebsiella oxytoca(Ko2),K. huaxiensis(Ko8) andK. grimontii(Ko6). The average nucleotide identity of Ko3 and Ko4 were 90.7% withK. huaxiensisand 95.5% withK. grimontii, respectively. In addition, three strains ofK. huaxiensis, a species so far described based on a single strain from a urinary tract infection patient in China, were isolated from cattle and human faeces. Biochemical and MALDI-ToF mass spectrometry analysis allowed differentiating Ko3, Ko4 and Ko8 from the otherK. oxytocaspecies. Based on these results, we propose the namesKlebsiella spallanzaniifor the Ko3 phylogroup, with SPARK_775_C1T(CIP 111695T, DSM 109531T) as type strain, andKlebsiella pasteuriifor Ko4, with SPARK_836_C1T(CIP 111696T, DSM 109530T) as type strain. Strains ofK. spallanzaniiwere isolated from human urine, cow faeces and farm surfaces, while strains ofK. pasteuriiwere found in faecal carriage from humans, cows and turtles.Accession numbersThe nucleotide sequences generated in this study were deposited in ENA and are available through the INSDC databases under accession numbersMN091365(SB6411T= SPARK775C1T), MN091366 (SB6412T= SPARK836C1T) and MN104661 to MN104677 (16S rRNA), MN076606 to MN076643 (gyrAandrpoB), and MN030558 to MN030567 (blaOXY). Complete genomic sequences were submitted to European Nucleotide Archive under the BioProject number PRJEB15325.AbbreviationsANI, average nucleotide identity; HCCA, a-cyano-4-hydroxycinnamic acid; isDDH,in silicoDNA-DNA hybridization; SCAI, Simmons citrate agar with inositol; MALDI57 ToF MS: Matrix-assisted laser desorption/ionization time of flight mass spectrometry