The Australian little penguin (Eudyptula novaehollandiae), from Australia and the Otago region of New Zealand, was initially described as Spheniscus novaehollandiae in 1826 and was later classified as Eudyptula minor novaehollandiae, a subspecies of the little penguin.

Like those of all penguins, the wings of Eudyptula species have developed into flippers used for swimming.

Eudyptula species typically grow to between 30 and 33 cm (12 and 13 in) tall and on average weigh 1.5 kg (3.3 lb). The head and upper parts are blue in colour, with slate-grey ear coverts fading to white underneath, from the chin to the belly. Their flippers are blue in colour. The dark grey-black beak is 3–4 cm long, the irises pale silvery- or bluish-grey or hazel, and the feet pink above with black soles and webbing. An immature individual will have a shorter bill and lighter upperparts.

Like most seabirds, the Eudyptula species have a long lifespan. The average for the species is 6.5 years, but flipper ringing experiments show that in very exceptional cases they may live up to 25 years in captivity.

Eudyptula minor does not have the distinct bright blue feathers that distinguish Eudyptula novaehollandiae. In addition, the vocalisation patterns of the New Zealand lineage located on Tiritiri Matangi Island vary from the Australian lineage located in Oamaru. Females are known to prefer the local call of the New Zealand lineage.

There are also behavioural differences that help differentiate these penguins. Those of the Australian lineage will swim together in a large group after dusk and walk along the shore to reach their nesting sites. This may be an effective predator avoidance strategy by traveling in a large group simultaneously. This has not been seen by those of the New Zealand lineage. Eudyptula minor only recently encountered terrestrial vertebrate predators, while Eudyptula novaehollandiae would have had to deal with carnivorous marsupials.

Also, Eudyptula novaehollandiae located in Australia will double brood. Birds will double brood by laying another clutch of eggs in hopes to increase their reproductive success. They complete this after the first clutch has successfully fledged. They may also do this due to the increasing sea surface temperatures and changing sources of food that are available. This behaviour has never been observed by those in New Zealand.