Two subspecies are here recognised in the geographically rare and taxonomically isolated Eucalyptus insularis Brooker. Eucalyptus insularis subsp. insularis is known only from North Twin Peak Island in the Recherche Archipelago, about 90 km east-south-east of Esperance. Eucalyptus insularis subsp. continentalis D.Nicolle & Brooker subsp. nov. is known only from several small populations near Cape Le Grand on the mainland, about 25 km south-east of Esperance, and differs from the type subspecies in its low shrubby habit, smaller adult leaves with obscure tertiary venation and irregularly-shaped oil glands, more strongly pendulous inflorescences, and its generally smaller buds and fruits.