The Auckland Shag (Phalacrocorax colensoi) or Auckland Islands Shag is a species of cormorant from New Zealand. The species is endemic to the Auckland Islands archipelago. It is a sedentary bird that primarily eats various crustaceans and fish. In recent years, roughly 1,000 pairs have been recorded. The Auckland Shag is a colonial nester, building sizeable nests of, among other items, grass, twigs and seaweed. The Auckland Shag lays three pale blue-green eggs in November-February. The incubation period for the Auckland Shag is 26-32 days.

The Auckland Shag is considered vulnerable by the IUCN due to its small population size and restricted global range. Only around 2000 Auckland Shags exist in their remote habitat.

The binomial name of this bird commemorates the naturalist William Colenso.