Multiple citizenship, dual citizenship, multiple nationality, or dual nationality is a person's
Some countries do not permit dual citizenship. This may be by requiring an applicant for
Most countries that permit dual citizenship still may not recognize the other citizenship of its nationals within its own territory, for example, in relation to entry into the country,
Up until the late 19th century, nations often decided whom they claimed as their citizens or subjects, and did not recognize any other nationalities they held. Many states did not recognize the right of their citizens to renounce their citizenship without permission, due to policies that originated with the feudal theory of perpetual allegiance to the sovereign. This meant that people could hold multiple citizenships, with none of their nations recognizing any other of their citizenships. Until the early modern era, when levels of migration were insignificant, this was not a serious issue. However, when non-trivial levels of migration began, this state of affairs sometimes led to international incidents, with countries of origin refusing to recognize the new nationalities of natives who had migrated, and when possible, conscripting natives who had naturalized as citizens of another country into military service. The most notable example was the
In the aftermath of the 1867
As a result, the theory of perpetual allegiance largely fell out of favor with governments during the late 19th century. With the consensus of the time being that dual citizenship would only lead to diplomatic problems, more governments began prohibiting it, and revoking the nationality of citizens holding another nationality. By the mid-20th century, dual nationality was largely prohibited worldwide, although there were exceptions. For example, a series of U.S. Supreme Court rulings permitted Americans born with citizenship in another country to keep it without losing their U.S. citizenship.
However, the consensus against dual nationality began to erode due to changes in social mores and attitudes. By the late 20th century it was becoming gradually accepted again. Many states were lifting restrictions on dual citizenship. For example, the