A Commonwealth citizen is a citizen of a Commonwealth of Nations member state. While most Commonwealth countries do not distinguish between them and the citizens of other countries, some grant limited rights and privileges. For example, in 14 Commonwealth countries, resident Commonwealth citizens are eligible to vote in elections. The status is most significant in the United Kingdom, where they are not considered foreign nationals under British law. They may be eligible to vote in elections, stand for public office, and access certain public services, subject to their right of abode (e.g. indefinite leave to remain).

In addition to voting and residency rights, in certain situations, Commonwealth citizens may receive consular assistance from fellow Commonwealth countries. Notably, they are entitled to emergency assistance from British embassies and consulates when in a non-Commonwealth country, where their own government has no diplomatic representation.

Commonwealth citizenship emerged gradually as the British Empire dissolved. Prior to 1949, all imperial subjects were classified as British subjects and owed allegiance to the Crown. Following the First World War, the Dominions, including Australia, Canada, Ireland, Newfoundland, New Zealand and South Africa, enacted their own nationality laws, but continued to recognise British subjecthood as a shared status with the United Kingdom and its colonies. However, increasing legislative divergence and growing Dominion autonomy led to the creation of Canadian citizenship in 1946, marking a formal separation from British subject status. This development, together with the forthcoming independence of India and Pakistan in 1947, prompted a comprehensive reform of nationality law.

The British Nationality Act 1948 redefined British subject as any citizen of the United Kingdom, its colonies, or other Commonwealth countries. Commonwealth citizen was also defined in this Act as having the same meaning. This change in naming indicated a shift in the base theory of British nationality, that allegiance to the Crown was no longer a requirement to hold British subject status. The change was also necessary to retain a number of newly independent countries that wished to become republics rather than retain the monarch as head of state. The common status of Commonwealth citizenship would instead be maintained voluntarily by the various members of the Commonwealth. Australian citizenship was created in 1949.

Initially, all Commonwealth citizens held the automatic right to settle in the United Kingdom. This was first restricted by Parliament with the Commonwealth Immigrants Act 1962, which imposed immigration controls on subjects originating from outside the core British Islands. The Immigration Act 1971 relaxed controls on patrials, those whose parents or grandparents were born in the United Kingdom, and effectively gave preferential treatment to Commonwealth citizens from white-majority countries.

Outside the United Kingdom, in some member states Commonwealth citizens also initially retained eligibility to vote in elections, to preferred paths to citizenship, and to welfare benefits. These privileges were removed on independence in most countries but retained in some. British subjects/Commonwealth citizens were eligible to vote in New Zealand until 1975, Canada at the federal level until 1975 (not fully phased out in provinces until 2006), and Australia until 1984 (though subjects on the electoral roll in that year are still eligible).

By the 1980s, most colonies of the Empire had become independent states. Parliament updated nationality law to reflect the more modest geographical boundaries of the United Kingdom and its remaining territories. The British Nationality Act 1981 redefined British subject in such a way that it no longer also meant Commonwealth citizen.

Commonwealth citizenship is acquired by virtue of being a citizen of a Commonwealth member state or, in the United Kingdom, a country listed in Schedule 3 of the British Nationality Act 1981. This list closely follows the composition of the organisation, but is not always the same. For example, the Maldives left the Commonwealth in 2016 before rejoining in 2020. The country was removed from Schedule 3 in 2017, but legislation was not updated to relist it until 2021. Conversely, although Zimbabwe has not been a part of the Commonwealth since 2003, Zimbabwean citizens retain Commonwealth citizenship because the country remains on Schedule 3.