stylistic:tone, information:classification
Population

Compared to the more populated and multi-ethnic North Island, the South Island has a smaller, more homogeneous resident population of 1,225,000 (June 2023).

The South Island had a population of 1,185,282 at the 2023 New Zealand census, an increase of 80,745 people (7.3%) since the 2018 census, and an increase of 180,882 people (18.0%) since the 2013 census. Of the total population, 202,311 people (17.1%) were aged under 15 years, 225,048 (19.0%) were 15 to 29, 538,965 (45.5%) were 30 to 64, and 218,958 (18.5%) were 65 or older.

At the 2018 census, there were 571,656 males and 577,914 females, giving a sex ratio of 0.99 males per female.

In the early years of European settlement in New Zealand, the South Island's overall percentage of the New Zealand population was far higher, equalling or even exceeding the population of the North Island. This was exacerbated by the New Zealand Wars and the Otago gold rush of the 1860s. Since that time, the South Island's population as a percentage of the country's total population has steadily decreased, with the population of the South island now being less than that of the North Island's largest city, Auckland. This growing disparity has stabilised in recent years, with both the 2013 and 2018 censuses showing the South Island to have a very similar percentage of the national population (around 23%–24%).