Six Gram negative, motile bacteria were isolated from rainbow trout (Oncorhynchus mykiss). The 16S rRNA sequence similarity values grouped them in thePseudomonas mandelii(strains P49, P50T, 154aTand P154b),Pseudomonas fluorescens(strain P115T) andPseudomonas koreensis(strain P155T) phylogenetic subgroups in the genusPseudomonas. The DNA G+C content ranged from 58.5 to 60 mol%. The strains were characterized phenotypically using API 20NE and Biolog GENIII tests, and chemotaxonomically by their whole-cell MALDI-TOF MS protein profiles and fatty acid contents. Multi-locus sequence analysis with four housekeeping gene sequences (rpoD,rpoB,gyrBand 16S rRNA) together with genome comparisons by average nucleotide identity and genome-to-genome distance calculations were performed. Results showed that the similarity values of these strains to known species type strains were lower than the thresholds established for species in the genusPseudomonas. Based on these data, we concluded that strains P49, P50T, P115T, P154aT, P154b and P155Tbelonged to four novel species. The names proposed are:Pseudomonas pisciumsp. nov. for strains P49 and P50Twith P50T(=CECT 30175T=CCUG 74871T) as the type strain;Pseudomonas pisciculturaesp. nov. for strain P115T(CECT 30173T=CCUG 74873T); Pseudomonas mucoidessp. nov. for strains P154aTand P154b with P154aT(=CECT 30177T=CCUG 74874T) as the type strain; andPseudomonas neuropathicasp. nov. for strain P155T(=CECT 30178T=CCUG 74875T).