Hypervirulent Klebsiella pneumoniae is a globally emerging pathogen that causes pyogenic liver abscesses. Hypervirulent strains are restricted to capsular serotypes K1 and K2 and are particularly associated with the clonal complex K1 CC23. To understand the evolution of hypervirulence, Struve et al. sequenced the genomes of 30 hypervirulent isolates and 35 non-hypervirulent isolates. A phylogenomic analysis indicated that CC23 isolates had undergone clonal expansion from a recent ancestor. Furthermore, several elements that may be associated with hypervirulence were identified, including a large virulence plasmid only present in hypervirulent strains. The virulence factors encoded by the plasmid include RmpA, a regulator of capsule production, and the siderophores aerobactin and salmochelin. Unique to the CC23 isolates was a recently acquired genomic island encoding the toxins microcin E492 and colibactin and the siderophore yersiniabactin.