In international relations, aid (also known as international aid, overseas aid, foreign aid or foreign assistance) is – from the perspective of governments – a voluntary transfer of resources from one country to another.

Aid may serve one or more functions: it may be given as a signal of diplomatic approval, or to strengthen a military ally, to reward a government for behaviour desired by the donor, to extend the donor's cultural influence, to provide infrastructure needed by the donor for resource extraction from the recipient country, or to gain other kinds of commercial access. Humanitarian and altruistic purposes are at least partly responsible for the giving of aid.