The Colony of New Zealand was a colony of the United Kingdom from 1841 to 1907. British authority was vested in a governor. The colony had three successive capitals: Okiato (or Old Russell) in 1841; Auckland from 1841 to 1865; and Wellington from 1865. Following the New Zealand Constitution Act 1852, the colony became a Crown colony with its first elected parliament in 1853. Responsible self-government was established in 1856 with the governor required to act on the advice of his ministers. In 1907, the colony became the Dominion of New Zealand.

Following the extension of the boundaries of New South Wales in January 1840 by Governor Gipps to include New Zealand, William Hobson left Sydney for New Zealand.

The Treaty of Waitangi—between Māori chiefs and British representatives of Queen Victoria—was subsequently signed on 6 February 1840. Hobson declared British sovereignty over the islands of New Zealand on 21 May 1840 in two separate declarations. In the first declaration, Hobson declared sovereignty over the North Island on the basis of cession following the Treaty of Waitangi. In the English version of the treaty, Māori ceded sovereignty and received the rights, privileges and protections of being British subjects. The Māori version of the treaty refers to kāwanatanga which is often translated today as governance or government. This point of difference has been a subject of much controversy and political debate. In the second declaration, Hobson declared British sovereignty over the South Island and Stewart Island on the basis of discovery in 1769 by James Cook.

The relationship between New Zealand and the Colony of New South Wales was formalised after a new definition of NSW's boundaries, that included New Zealand, arrived from London on 15 June 1839. It stated that the NSW colony would include "any territory which is or may be acquired in sovereignty by Her Majesty ... within that group of Islands in the Pacific Ocean, commonly called New Zealand." This made Lieutenant-Governor Hobson answerable to his superior, the governor of New South Wales. By letters patent, the British government issued the Charter for Erecting the Colony of New Zealand on 16 November 1840. The Charter stated that the Colony of New Zealand would be established as a de jure Crown colony separate from New South Wales on 3 May 1841.

In its early years, British effective control over the whole colony was limited. Connecting control with sovereignty, the historian James Belich, says sovereignty fell into two categories: nominal (meaning the de jure status of sovereignty, but without the power to govern in practice) and substantive (in which sovereignty can be both legally recognised and widely enforced without competition). He wrote: "Certainly, for many years after 1840, 'nominal sovereignty' was much closer to the reality. This ambiguity was a source of friction. The British imagined that they were entitled to govern the Maoris in fact as well as name, although [William Hobson and Robert FitzRoy] were sufficiently realistic to grasp that substantive sovereignty could not be applied comprehensively overnight."

With the establishment of the Crown colony, Hobson became governor of New Zealand. The first organs of the New Zealand Government were also established to assist the governor: an Executive Council and a (General) Legislative Council.

The Executive Council consisted of the attorney-general, colonial secretary, and colonial treasurer. The Legislative Council consisted of the governor, Executive Council, and three justices of the peace appointed by the governor. The Legislative Council had the power to issue laws called Ordinances.

The colony was initially divided into three provinces: New Ulster Province (the North Island), New Munster Province (the South Island), and New Leinster Province (Stewart Island).