We present a genome assembly from a specimen of Blennius ocellaris (the butterfly blenny; Chordata; Actinopteri; Blenniiformes; Blenniidae). The genome sequence spans 728.70 megabases. Most of the assembly is scaffolded into 24 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.5 kilobases in lengt