A foreign worker (cf expatriate), is a person who works in a country other than the one of which he or she is a citizen.

The term, in its broadest sense, may cover a multitude of cases. Most commonly, it refers to economic migrants, who typically travel (either legally or illegally) to a country with a stronger economy than the one in which they hold citizenship. Those that are legal may be either full-fledged immigrants or may be in the host country on a conditional work permit. Sometimes the host country sets up a real advertising program in order to invite foreign workers, as did the Federal Republic of Germany in the 1960s, when over one million of so-called guest workers (Gastarbeiter) were attracted, mostly from Italy, Spain or Turkey.

The term can also include international experts working out-of-country (usually, but not always, legally) and any number of cases in between. For example, in recent years in the USA there has been much controversy over whether H-1B visas, intended to bring highly skilled workers to fill gaps in the domestic labor pool, are instead being used to bring in skilled, but otherwise unexceptional, economic migrants as cheap labor to fill jobs that could readily be filled domestically.

See also Immigration.