The boundaries of the Colony of New Zealand are extended by the UK to include the Cook Islands.

The Cook Islands (Cook Islands Mori: Kki 'irani) is a self-governing island country in the South Pacific Ocean in free association with New Zealand. It comprises 15 islands whose total land area is 240 square kilometres (93 sq mi). The Cook Islands' Exclusive Economic Zone (EEZ) covers 1,960,027 square kilometres (756,771 sq mi) of ocean.New Zealand is responsible for the Cook Islands' defence and foreign affairs, but these responsibilities are exercised in consultation with the Cook Islands. In recent times, the Cook Islands have adopted an increasingly independent foreign policy. Cook Islanders are citizens of New Zealand, but they also have the status of Cook Islands nationals, which is not given to other New Zealand citizens. The Cook Islands have been an active member of the Pacific Community since 1980.

The Cook Islands' main population centres are on the island of Rarotonga (13,007 in 2016), where there is an international airport. The census of 2016 put the total population at 17,459. There is also a larger population of Cook Islanders in New Zealand itself: in the 2018 New Zealand census, 80,532 people said they were Cook Islanders, or of Cook Islands descent.With over 168,000 visitors travelling to the islands in 2018, tourism is the country's main industry, and the leading element of the economy, ahead of offshore banking, pearls, and marine and fruit exports.

The Colony of New Zealand was a British colony that existed in New Zealand from 1841 to 1907. It was created as a Crown colony. The power of the British government was vested in the governor of New Zealand, but the colony was granted self-government in 1852. The New Zealand Constitution Act 1852 was passed and the first parliament was elected in 1853; the first responsible government was formed in 1856. The Colony of New Zealand had three capitals: Old Russell (1841), Auckland (1841–1865), and Wellington (since 1865). In 1907, the colony became the Dominion of New Zealand with more explicit recognition of self-government within the British Empire.