stateless person
Legal and formal term for a person who is not considered a national by any state.
As a stateless person, he could not get a passport issued by any country.
国籍 means 'nationality'; 無国籍者 is a person without it.
難民 is a refugee, who may or may not be stateless; 無国籍者 specifically lacks any nationality.
Compound of 無 (without), 国籍 (nationality), and 者 (person).