A foreign legion is a military force originally established by a monarch, consisting of foreigners who are not normally subjects of the king/queen. As their members are on duty all the time, they are not of the same structure as a regiment. Many countries, including Britain (sc., "King's German Legion") had these before the twentieth century. The only remaining ones are those of France and Spain; the phrase foreign legion in English generally refers to the French one.

• French Foreign Legion
• Spanish Foreign Legion