- Italy--Syracuse2
- Italy--Volterra2
- Iṣfahānī, Maḥmūd ibn ʻAbd al-Raḥmān, 1275 or 1276-1348 or 1349. Tasdīd al-qawāʼid fī sharḥ Tajrīd al-ʻaqāʼid2
- Jainism2
- Jawī Zādah, Muḥammad ibn Ilyās, -1547 or 1548. Risālah fī al-masḥ ʻalá al-khuffayn2
- Jaʻbarī, Ṣāliḥ ibn Thāmir, d. 1306. Naẓm al-laʼālī2
- Jewish astrology2
- Jewish drama2
- Jewish families2
- Jewish hymns2
- Jewish illumination of books and manuscripts2
- Jewish martyrs2
- Jewish prayers for rain2
- Jewish travelers2
- Jewish women2
- Jews--Legal status, laws, etc.2
- Jews--Politics and government2
- Jihad2
- John I, King of Portugal, 1357-14332
- Juana, of Austria, Princess of Portugal, 1535-15732