How to Say "Nationality" in Japanese

国籍

kokuseki[ko̞kɯ̟̊se̞kʲi]

The Japanese word for "nationality" is 国籍 (kokuseki).

国籍 is a noun used to describe the legal membership of a nation or state.

Meaning: membership of a nation or state (noun)

What does it mean word for word?

The word 国籍 is composed of 国, meaning "country" and 籍, meaning "register" or "record".

kokuseki

The character 籍 (seki) used in 国籍 originally referred to a bamboo slip used for writing. This reflects an ancient system of recording census data on wooden strips.
Japan is one of the few countries that strictly prohibits dual 国籍. People who acquire a second nationality are generally required to renounce their Japanese citizenship by age 22.
While 国籍 (kokuseki) refers to legal nationality, Japanese people often use 出身 (shusshin), meaning 'place of departure', to describe where they are from in social settings.

私はフランス国籍ですが、出身はベトナムです。
I have the French nationality, but I'm from Vietnam.
This sentence is useful for showing how to state your nationality and your place of origin.
Tatoeba #2461484 by verbum, translation #2592709 by WestofEden
国籍不明の飛行機
An airplane of unknown nationality
This sentence is useful for describing an object, such as an airplane, with an unknown nationality.
Wiktionary
私はフランス国籍を持っているがベトナム出身です。
I have French nationality but Vietnamese origins.
This sentence is useful for expressing the possession of a nationality and one's origins.
Tatoeba #136180 by HARUMI, translation #2142 by pyrachi

Yota and Himari are filling out an application form together.

陽太 Yota

ここの国籍の欄には何を書けばいい？
Koko no kokuseki no ran ni wa nani o kakeba ii?
What should I write in this nationality column?
陽葵 Himari

自分の国籍を書いてください。
Jibun no kokuseki o kaite kudasai.
Please write your nationality.
陽太 Yota

日本の国籍と書いていいよね？
Nihon no kokuseki to kaite ii yo ne?
It's okay to write Japanese nationality, right?
陽葵 Himari

はい、それで大丈夫です。
Hai, sore de daijōbu desu.
Yes, that is fine.

Sources

⭐Share⭐ to appreciate human effort 🙏