noun
dual citizen; person with dual nationality
Refers to a person who legally holds citizenship of two countries.
彼は日本とアメリカの二重国籍者です。
He is a dual citizen of Japan and the United States.
二重国籍 is the state of dual nationality, while 二重国籍者 refers to the person who holds it.
Compound of 二重 (double) + 国籍 (nationality) + 者 (person).