Dedicated to the Immaculate Conception
- December 1
- St. Edmund Campion, English Martyr
- St. Nahum the Minor Prophet
- December 2
- St. Bibiana, Martyr
- December 3
- St. Francis Xavier, Jesuit Missionary
- St. Sophonias the Minor Prophet
- December 4
- St. Peter Chrysologus
- St. Barbara, Martyr (Auxiliary Saint)
- December 5
- St. Sabbas, Martyr
- December 6
- St. Nicholas of Myra, Bishop
- December 7
- Vigil of the Immaculate Conception of the Blessed Virgin Mary
- St. Ambrose, Bishop
- December 8
- Feast of the Immaculate Conception of the Blessed Virgin Mary (Holyday of Obligation)
- December 9
- St. Juan Diego
- St. Leocadia
- December 10
- Our Lady of Loretto
- Pope St. Melchiades, Martyr
- December 11
- Pope St. Damasus I
- December 12
- Our Lady of Guadalupe, Patron of the Americas
- December 13
- St. Lucy, Virgin and Martyr
- December 14
- SS. Nicasius (Bishop), Eutropia (Virgin), and Companions, Martyrs
- St. Venantius Fortunatus, Bishop
- Saintly Birthday of St. John of The Cross (Exiting this world)
- December 15
- St. Christiana, Virgin
- St. Mesmin, Abbot
- December 16
- St. Eusebius, Bishop
- SS. Azarias, Ananias, and Misael, Daniel’s Companions
- December 17 (O Sapientia)
- St. Lazarus, Brother of SS. Mary Magdalene and Martha
- December 18 (O Adonai)
- The Expectation of the Blessed Virgin Mary
- St. Gatian, Bishop
- December 19 (O Radix Jesse)
- St. Fausta, Mother of St. Anastasia, Martyr
- SS. Nemesius and Companions, Martyrs
- Pope Bl. Urban V
- December 20 (O Clavis David)
- St. Dominic de Silos
- December 21 (O Oriens)
- St. Thomas the Apostle, Martyr
- December 22 (O Rex Gentium)
- St. Flavian, Father of St. Bibiana, Martyr
- St. Ischyrion of Alexandria, Martyr
- St. Frances Xavier Cabrini (Feast outside the United States)
- December 23 (O Emmanuel)
- St. Yvo of Chartres
- St. Victoria
- December 24 – Vigil of Christmas (No Meat)
- SS. Adam and Eve, Our First Parents
- December 25 – Christmas, The Feast of the Nativity of Our Lord, Jesus Christ (Navidad)
- Commemoration of St. Anastasia, Martyr
- December 26
- St. Stephen, Protomartyr
- December 27
- St. John the Apostle and Evangelist
- December 28
- The Holy Innocents, Martyrs (Mt. ii)
- St. Baruch (who assisted St. Jeremias the Prophet)
- December 29
- St. David, King of Israel and Prophet
- St. Thomas a Becket, Bishop of Canterbury and Martyr
- December 30
- St. Sabinus, Bishop and Martyr
- December 31
- Pope St. Sylvester I
- St. Catherine Laboure, Mystic