multiple citizenship; dual nationality
Refers to the legal status of holding citizenship in more than one country. Often discussed in contexts of nationality law and international relations.
Multiple citizenship is not recognized in Japan.
Because he has multiple citizenship, he holds several passports.
二重国籍 specifically means dual citizenship (two countries), while 多重国籍 is a broader term for multiple citizenship (three or more).
Compound of 多重 (multiple) + 国籍 (nationality).