word | | Country name |
| conventional | Jamaica | conventional long form: none conventional short form: Jamaica |
| conventional | Jan Mayen | conventional long form: none conventional short form: Jan Mayen |
| conventional | Japan | conventional long form: none conventional short form: Japan local long form: Nihon-koku/Nippon-koku local short form: Nihon/Nippon |
| conventional | Jersey | conventional long form: Bailiwick of Jersey conventional short form: Jersey |
| conventional | 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 |
| conventional | Kazakhstan | conventional long form: Republic of Kazakhstan conventional short form: Kazakhstan local long form: Qazaqstan Respublikasy local short form: Qazaqstan former: Kazakh Soviet Socialist Republic |
| conventional | Kenya | conventional long form: Republic of Kenya conventional short form: Kenya local long form: Republic of Kenya/Jamhuri ya Kenya local short form: Kenya former: British East Africa |
| conventional | Kiribati | conventional long form: Republic of Kiribati conventional short form: Kiribati local long form: Republic of Kiribati local short form: Kiribati note: pronounced keer-ree-bahss former: Gilbert Islands |
| conventional | Korea, North | conventional long form: Democratic People's Republic of Korea conventional short form: North Korea local long form: Choson-minjujuui-inmin-konghwaguk local short form: Choson abbreviation: DPRK |
| conventional | Korea, South | conventional long form: Republic of Korea conventional short form: South Korea local long form: Taehan-min'guk local short form: Han'guk abbreviation: ROK |
| conventional | Kosovo | conventional long form: Republic of Kosovo conventional short form: Kosovo local long form: Republika e Kosoves (Republika Kosovo) local short form: Kosova (Kosovo) |