- Ibn al-Nafīs, ʻAlī ibn Abī al-Ḥazm, 1210 or 1211-1288. Mūjiz al-Qānūn1
- Ibn al-Nāẓim, Muḥammad ibn Muḥammad, d. 1287 or 8. Sharḥ al-Alfīyah1
- Ibn al-Sāʻātī, Aḥmad ibn ʻAlī, 1254-1294 or 1295. Badīʻ al-niẓām al-jāmiʻ bayna Kitāb al-Bazdawī wa-al-aḥkām1
- Ibn ʻAbd al-Barr, Yūsuf ibn ʻAbd Allāh, 978 or 979-1071. Jāmiʻ bayān al-ʻilm wa-faḍlih1
- Ibn ʻAqīl, ʻAbd Allāh ibn ʻAbd al-Raḥmān, 1294?-1367. Sharḥ al-Alfīyah1
- Ibn Ḥajar al-ʻAsqalānī, Aḥmad ibn ʻAlī, 1372-1449. Tahdhīb al-Tahdhīb.--Abridgment1
- Ibn Ḥijjah al-Ḥamawī, Taqī al-Dīn Abū Bakr ibn ʻAlī, -1434. Badīʻīyah1
- Ibn Ḥijjah al-Ḥamawī, Taqī al-Dīn Abū Bakr ibn ʻAlī, -1434. Badīʻīyat1
- Ildobrandini, Geronimo1
- Illegible markings1
- Illumination of books and manuscripts, Renaissance1
- Immortality1
- Indexes1
- Indulgences (Canon law)1
- Inheritance and succession (Canon law)1
- Inheritance and succession (Roman law)1
- Initials (Abbreviations)1
- Innocent III, Pope, 1160 or 1161-12161
- Innocent VIII, Pope, 1432-14921
- Interdict (Canon law)1