The complete genome sequence of a novel megrivirus of the family Picornaviridae was determined from nucleic acid extracted from a pool of six faecal specimens of Adélie penguins. The samples were collected near Bellingshausen Station, King George Island of the South Shetland Islands, Antarctica. Penguin megrivirus is the first megrivirus with a predicted L protein. It has an L-3-5-4 genome layout, a type IV IRES, and a long 3' untranslated region of 668 nt.