The natural history of New Zealand began when the landmass Zealandia broke away from the supercontinent Gondwana in the Cretaceous period. Before this time, Zealandia shared its past with Australia and Antarctica. Since this separation, the New Zealand landscape has evolved in physical isolation, although much of its current biota has more recent connections with species on other landmasses. The exclusively natural history of the country ended in about 1300 AD, when humans first settled, and the country's environmental history began. The period from 1300 AD to today coincides with the extinction of many of New Zealand's unique species that had evolved there.

The environment of New Zealand is characterised by an endemic flora and fauna which has evolved in near isolation from the rest of the world. The main islands of New Zealand span two biomes, temperate and subtropical, complicated by large mountainous areas above the tree line. There are also numerous smaller islands which extend into the subantarctic. The prevailing weather systems bring significantly more rain to the west of the country. New Zealand's territorial waters cover a much larger area than its landmass and extend over the continental shelf and abyssal plateau in the South Pacific Ocean, Tasman Sea and Southern ocean.