- Jiří, z Poděbrad, King of Bohemia, 1420-14711
- Juan II, King of Castile and Leon, 1405-14541
- Juana, la Loca, Queen of Castile, 1479-15551
- Juana, of Austria, Princess of Portugal, 1535-15731
- Judaism--Customs and practices1
- Judgment Day (Islam)1
- Jugurthine War (111-105 B.C.)1
- Justice, Administration of1
- Jāmiʻ al-Muẓaffarī (Damascus, Syria)1
- Jāmiʻ al-ṣaḥīḥ (Muslim ibn al-Ḥajjāj al-Qushayrī)1
- Kanz al-wuṣūl ilá maʻrifat al-uṣūl (Bazdawī, ʻAlī ibn Muḥammad)1
- Karaite manuscripts1
- Karaitic literature1
- Kaʻbah (Mecca, Saudi Arabia)1
- Kemalpaşazade, 1468 or 1469-15341
- Ketubah1
- Khamrīyah (Ibn al-Fāriḍ, ʻUmar ibn ʻAlī)1
- Khaṭīb al-Baghdādī, Abū Bakr Aḥmad ibn ʻAlī, 1002-1071. Asmāʼ al-mubhamah fī al-anbāʼ al-muḥkamah1
- Kings and rulers--Duties1
- Kings and rulers--Heraldry1