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 721,801 orthologous groups in 1133 species, covering 4,396,591 proteins (built from 5,214,234 proteins).