Jus sanguinis (Latin: right of blood) is a principle of nationality law by which citizenship is not determined by place of birth but by having one or both parents who are citizens of the state. Children at birth may automatically be citizens if their parents have state citizenship or national identities of ethnic, cultural or other origins. Citizenship can also apply to children whose parents belong to a diaspora and were not themselves citizens of the state conferring citizenship. This principle contrasts with jus soli (Latin: right of soil).

At the end of the 19th century, the French-German debate on nationality saw the French, such as Ernest Renan, oppose the German conception, exemplified by Johann Fichte, who believed in an "objective nationality", based on blood, race or language. Renan's republican conception, but perhaps also the presence of a German-speaking population in Alsace-Lorraine, explains France's early adoption of jus soli. Many nations have a mixture of jus sanguinis and jus soli, including the United States, Canada, Israel, Greece, Ireland, and recently Germany.