- Manuscripts, Spanish136
- Maps2
- Margarita, de Austria, Queen, consort of Philip III, King of Spain, 1584-16111
- Marginalia1
- Marriage (Canon law)1
- Marriage (Canon law)--Dispensations1
- Marriage law1
- Marshals1
- Marucelli, Benedetto1
- Marucelli, Francesco, 1625-17031
- Mary, Blessed Virgin, Saint4
- Massachusetts--Boston10
- Mathematical instruments1
- Mathematics1
- Mayenne, Charles de Lorraine, Duc de, 1554-16111
- Medicine1
- Medina Sidonia, Alonso Pérez de Guzmán, duque de, 1550-16191
- Medina Sidonia, Juan Alonso de Guzmán, Duque de, -15581
- Medina, Francisco de, 1544-16151
- Meditations1