The Province of Otago comprehends all that part of New Zealand south of the river Waitaki and a line from Lake Ohau through Mount Aspiring to Big Bay on the West Coast, and it contains, with Stewart Island, an area of about 20,876 square miles. It is essentially a mountainous country, the only very extensive flat land being the Southland plains, between the Hokanui and Moonlight ranges and the sea. Besides these, however, there are many smaller areas of flat or undulating country, and in the interior the Maniototo Plains, the Idaburn Valley, and Manuherika Plains are of considerable extent.

The highest land in the Province is situated in the north-west corner from Mt. Aspiring (9940ft), through Mt. Edward (8459ft), Mt. Tyndall (8116), Mt. Ansted (8157ft), Centaur Peak (8284ft), Cosmos Peak (8000ft), and Mt. Earnslaw (9165ft), to Mt. Christina (8475). Southward and eastward of this the mountains lower until they assume, towards the sea, with few exceptions, the form of rolling downs, averaging about 1500 feet above the sea level. Along the west coast, however, the mountains never lose their rugged character, and maintain an altitude in the highest peaks of between 4000 and 5000 feet as far as the south-west corner of the Province.