Mountains are one of the dominant features in the New Zealand landscape. Sixty percent of the South Island, and twenty percent of the North Island, can be classified as mountain land. Most of it stands over 600 metres altitude (2000 feet), and most is steep land.

The mountains in New Zealand result from the collision between the Australian and Pacific tectonic plates, and their location follows the boundary of the two plates. Thus a continuous chain of mountains forms the axial part of the South Island, extending over 750 km (500 miles) from the Kaikoura Ranges, through the length of the Southern Alps, to the southernmost corner of Fiordland. In the east of the North Island the axial ranges extend in a uninterrupted chain, from Wellington and the Rimutaka Ranges in the south to the Tararua, Ruahine, Kaimanawa-Kaweka, and Raukumara Ranges in the north. While located outside the axial area, the other major mountain ranges of New Zealand also originate in the same plate tectonic process: they are the Central Otago ranges, Paparoa, Victoria, North-west and East Nelson in the South Island, and the two large volcanic centres of Mt Egmont, and Ruapehu-Tongariro in the North Island.

The distinctive character of the mountains of New Zealand result from the combination of the following factors:

- the plate tectonic processes already mentioned,
- climatic conditions, in particular the high precipitation and rainfall produced by the combination of a dominant westerly flow with the high barrier of the mountain ranges,
- the nature and variations of rock types and geological structures,
- the action in the landscape of the glaciers and other agents that were at work during the glacial ages.

Finally, the specific character of New Zealand's native vegetation also contributes to the character of the mountains.