eggNOG (evolutionary genealogy of genes: Non-supervised Orthologous Groups) is a database of orthologous groups of genes. The orthologous groups are annotated with functional description lines (derived by identifying a common denominator for the genes based on their various annotations), with functional categories (i.e derived from the original COG/KOG categories).

eggNOG's database currently counts 224,847 orthologous groups in 630 species, covering 2,242,035 proteins (built from 2,590,259 proteins) of which 1,966,709 are annotated.