Pichia pastoris was reassigned earlier to the genus Komagataella following phylogenetic analysis of gene sequences. Since that time, two additional species of Komagataella have been described, K. pseudopastoris and K. phaffii. Because these three species are unlikely to be resolved from the standard fermentation and growth tests used in yeast taxonomy, the identity of biotechnologically important strains of K. pastoris was determined from multigene sequence analyses. Results from this study show that the strain of 'Pichia pastoris' commonly used in gene expression studies is actually K. phaffii.