- Illumination of books and manuscripts, Gothic1
- Illumination of books and manuscripts--Technique1
- In Coena Domini bulls1
- Indians, Treatment of1
- Indulgences1
- Indulgences (Canon law)1
- Influence (Literary, artistic, etc.)1
- Inheritance and succession (Canon law)1
- Inheritance and succession (Roman law)1
- Innocent IV, Pope, approximately 1200-12541
- Innocent VIII, Pope, 1432-14921
- Institutiones oratoriae (Quintilian)1
- Intellectual life1
- Interdict (Canon law)1
- Interfaith relations1
- Inventions1
- Ireland1
- Isabella I, Queen of Spain, 1451-15041
- Isagoge (Porphyry)1
- Islam1