Governor-general (plural governors-general), or governor general (plural governors general), is the title of an official, most prominently associated with the British Empire and the Commonwealth. In the context of the governors-general and former British colonies, governors-general continue to be appointed as viceroy to represent the monarch of a personal union in any sovereign state over which the monarch does not normally reign in person (non-UK Commonwealth realm). In the British Empire, governors-general were appointed on the advice of the government of the United Kingdom and were often British aristocracy, but in the mid-twentieth century they began to be appointed on the advice of the independent government of each realm and be citizens of each independent state.

Governors-general have also previously been appointed in respect of major colonial states or other territories held by either a monarchy or republic, such as Japan, Korea, Taiwan and France in Indochina.

In modern usage, in the context of governors-general and former British colonies, the term governor-general originated in those British colonies that became self-governing within the British Empire. Before World War I, the title was used only in federated colonies in which its constituents had had governors prior to federating, namely Canada, Australia, and the Union of South Africa. In these cases, the Crown's representative in the federated Dominion was given the superior title of governor-general. The first exception to this rule was New Zealand, which was granted Dominion status in 1907, but it was not until 28 June 1917 that Arthur Foljambe, 2nd Earl of Liverpool, was appointed the first governor-general of New Zealand.

Since the 1950s, the title governor-general has been given to all representatives of the sovereign in independent non-UK Commonwealth realms. In these cases, the former office of colonial governor was altered (sometimes for the same incumbent) to become governor-general upon independence, as the nature of the office became an entirely independent constitutional representative of the monarch rather than a symbol of previous colonial rule. In these countries the governor-general acts as the monarch's representative, performing the ceremonial and constitutional functions of a head of state.

The only other nation which currently uses the governor-general designation is Iran, which has no connection with any monarchy or the Commonwealth. In Iran, the provincial authority is headed by a governor general (Persian: استاندار ostāndār), who is appointed by the minister of the interior.

Until the 1920s, governors-general were British subjects, appointed on the advice of the British government, who acted as agents of the British government in each Dominion, as well as being representatives of the monarch. As such they notionally held the prerogative powers of the monarch, and also held the executive power of the country to which they were assigned. The governor-general could be instructed by the colonial secretary on the exercise of some of his functions and duties, such as the use or withholding of royal assent from legislation; history shows many examples of governors-general using their prerogative and executive powers. The monarch or imperial government could overrule any governor-general, though this could often be cumbersome, due to the remoteness of the territories from London.

The governor-general was also usually the commander-in-chief of the armed forces in their territory and, because of the governor-general's control of the military, the post was as much a military appointment as a civil one. The governors-general are entitled to wear a unique uniform, which is not generally worn today. If of the rank of major general, equivalent or above, they were entitled to wear that military uniform.

Following the Imperial Conference, and subsequent issuing of the Balfour Declaration in 1926, the role and responsibilities of the governor-general began to shift, reflecting the increased independence of the Dominions (which were in 1952 renamed realms; a term which includes the UK itself). As the sovereign came to be regarded as monarch of each territory independently, and, as such, advised only by the ministers of each country in regard to that country's national affairs (as opposed to a single British monarch ruling all the Dominions as a conglomerate and advised only by an imperial parliament), so too did the governor-general become a direct representative of the national monarch only, who no longer answered to the British government. The report resulting from the 1926 Imperial Conference stated: "It is an essential consequence of the equality of status existing among the members of the British Commonwealth of Nations that the Governor General of a Dominion is the representative of the Crown, holding in all essential respects the same position in relation to the administration of public affairs in the Dominion as is held by His Majesty the King in Great Britain, and that he is not the representative or agent of His Majesty's Government in Great Britain or of any Department of that Government." These concepts were entrenched in legislation with the enactment of the Statute of Westminster in 1931, and governmental relations with the United Kingdom were placed in the hands of a British High Commissioner in each country.