The New Zealand kākā (Nestor meridionalis) is a large species of parrot of the family Strigopidae found in New Zealand's native forests across the three main Islands of New Zealand. The species is often known by the abbreviated name kākā, although it shares this name with the recently extinct Norfolk kākā and Chatham kākā. Two subspecies of New Zealand kākā are recognised. It is endangered and has disappeared from much of its former range, though the re-introduction of North Island kākā at Zealandia in Wellington has led to an increasing population of the birds across the city.

The New Zealand kākā was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the parrots in the genus Psittacus and coined the binomial name Psittacus meridionalis. The specific epithet meridionalis is Latin meaning "southern". Gmelin based his description on the "Southern brown parrot" from New Zealand that had been described in 1781 by the English ornithologist John Latham in his book A General Synopsis of Birds. Latham had examined a preserved specimen in the Leverian Museum in London. The New Zealand kākā is now placed in the genus Nestor that was introduced in 1830 by René Lesson.

There are two subspecies, the North Island kākā, Nestor meridionalis septentrionalis, and the South Island kākā, N. m. meridionalis, although more recent research has ruled out allopatric subspeciation. The Māori language name kākā means "parrot", possibly related to kā, 'to screech'.

The genus Nestor contains four species, two of which are extinct: the New Zealand kākā (Nestor meridionalis), the kea (N. notabilis), the extinct Norfolk kākā (N. productus), and the extinct Chatham kākā (N. chathamensis). All four are thought to stem from a "proto-kākā", dwelling in the forests of New Zealand five million years ago. The closest living relative to the Nestor genus is the kākāpō (Strigops habroptilus). Together, they form the parrot superfamily Strigopoidea, an ancient group that split off from all other Psittaciformes before their radiation.

The kākā's closest living relative is the kea; the kea and kākā became separate species 1.72 million years ago due to ecological divergence. This likely occurred due to changes in the climate during the Pleistocene that drove the kākā to specialise in more forested environments and the kea to specialise in alpine and other habitats. This is why kākā are found in more forested areas with complex canopies compared to the kea. There is also more genetic diversity within the kākā compared to the kea and kākāpō.

The New Zealand kākā is a medium-sized parrot, measuring 45 cm (18 in) in length and weighing from 390 to 560 g (14 to 20 oz), with an average of 452 g (0.996 lb). It is closely related to the kea, but has darker plumage and is more arboreal. The forehead and crown are greyish-white and the nape is greyish brown. The neck and abdomen are more reddish, while the wings are more brownish. Both sub-species have a strongly patterned brown/green/grey plumage with orange and scarlet flashes under the wings; colour variants that show red to yellow colouration especially on the breast are sometimes found.

The calls include a harsh ka-aa and a whistling u-wiia.

Kākā beak morphology also differs slightly from its closest relatives, the kea and kākāpō. The rhinotheca (upper part of the beak) of the kākā is narrower than the kākāpo and slightly longer. However, it is not as long and sharp as the rhinotheca seen in kea. Therefore, the kākā's bill is between the kea and kākāpō in length, sharpness, and width.