Although broadly speaking the designation oyatoi-gaikokujin also included the employees of foreign diplomatic missions in Japan as well as the (foreign) guards at the foreign settlements, for the purposes of this article the term will be used only for those foreigners who were employed by the Japanese government in order to foster the learning of new technologies and scholarship from Europe and the United States.
広義では在外公館で雇用されていた者や、外国人居留地の警備に当たった者なども含まれるが、本項では日本が欧米から新しい技術や知識を学ぶために雇用した人物について述べる。