Jamaica
conventional long form: none
conventional short form: Jamaica

Jan Mayen
conventional long form: none
conventional short form: Jan Mayen

Japan
conventional long form: none
conventional short form: Japan

Jarvis Island
conventional long form: none
conventional short form: Jarvis Island

Jersey
conventional long form: Bailiwick of Jersey
conventional short form: Jersey

Johnston Atoll
conventional long form: none
conventional short form: Johnston Atoll

Jordan
conventional long form: Hashemite Kingdom of Jordan
conventional short form: Jordan
local long form: Al Mamlakah al Urduniyah al Hashimiyah
local short form: Al Urdun
former: Transjordan

Juan de Nova Island conventional long form: none conventional short form: Juan de Nova Island local long form: none local short form: Ile Juan de Nova

Kazakhstan
conventional long form: Republic of Kazakhstan
conventional short form: Kazakhstan
local long form: Qazaqstan Respublikasy
local short form: none
former: Kazakh Soviet Socialist Republic

Kenya
conventional long form: Republic of Kenya
conventional short form: Kenya
former: British East Africa