May 1
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Achatius; Ache; Acheolus; Acheul; Achius & Acheolus; Aehgein of Fore; Brioc; James the Just; Saint Joseph; Peregrine Laziosi; Philip the Apostle; Ultan of Ardbraccan; Philip and James, Apostles;

May 2
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Achumdemas; Aedhan McCuamsie; Athanasius of Alexandria; Mafalda of Portugal;

May 3
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Abhai (saint); Abhai the Bishop; Aedhan; Pope Alexander I; Finding of the Cross; Philip the Apostle and James the Less; Shmouni & her sons; Theodosius of Kiev;

May 4
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Ada; Adrechildis; Agilbert of Angers; English Saints and Martyrs of the Reformation Era; Saint Florian; Gotthard of Hildesheim; Saint Pelagia;

May 5
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Abraham (Ethiopian); Adrianus Monsenski; Ascension; Hilary of Arles; Jutta of Kulmsee; Pope Pius V;

May 6
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Ache; John the Evangelist;

May 7
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Achatius of the Haptascalon; Achatius the Centurion; Agathius the Centurion; John of Beverley; Nil Sorsky; Stanislaus of Szczepanów;

May 8
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Achatius the Centurion; Agathius the Centurion; Arsenius the Great; Pope Benedict II; Julian of Norwich; Peter of Tarentaise; Victor of Milan;

May 9
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Saint Christopher; Gregory of Nazianzus;

May 10
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Achates; Achatius; Achatius the Centurion; Aedh of Kildare; Agathius the Centurion; Antoninus of Florence; John of Avila; Simon the Zealot;

May 11
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Abgar V of Edessa; Achilles, Sipponius, Epimenus & Nereus; Achius and Acheolus; Adalgar of Hamburg; Adger; Aelgnei; Agathander; Agathimber of Metz; Comgall; Saint Cyril; Saints Cyril and Methodius; Saint Methodius;

May 12
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Achaicus; Achilleus; Epiphanius of Salamis; Florence Nightingale; Patriarch Germanus I of Constantinople;

May 13
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Abban the Hermit; Ager; Agnes and Disciola; Agrippa; Agrippa; Andrew Hubert Fournet; Julian of Norwich; Robert Bellarmine;

May 14
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Adauctus; Addaeus; Addai; Adeltrudis; Adeodatus; Aegydius Valledaris; Afranus; Aglae; Agrippa; Magdalen of Canossa; Maria Mazzarello; Saint Matthias; Michael Garicoïts; Pachomius;

May 15
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Achilles of Larissa; Achillius of Larissa; Adalsindis; Jean-Baptiste de la Salle; Pachomius; Pentecost; Virgin Mary;

May 16
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Aaron (Copt); Aba of Kaskhar; Abda, Abdallah, Abdias, Abdjesus; Abdjesus; Abdjesus of Kashkar; Abdha; Abercius and Helena; Abraham; Brendan; Caroline Chisholm; John of Nepomuk; Maris, Martha, Abachum and Audifax; Simon Stock;

May 17
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Adrion, Victor & Basilla; Aemilianus of Vercelli; Agapius; Agathocles; Agrippina; Robert Bellarmine;

May 18
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Aelgyfa; Aghna; Elgifa; Eric IX of Sweden;

May 19
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Aemilius, Basilius, Praetextata, Basia & Partinus; Agrippa; Agrippa and Laurentius; Pope Celestine V; Dunstan; Helena of Constantinople; Ivo of Kermartin;

May 20
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Abercius and Helena; Alcuin; Bernardino of Siena; Friday of Gold; Ivo of Chartres; Æthelberht II of East Anglia;

May 21
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Abraham of Egypt; Adalric; Adelphius; Adrianus; Agapitus Markushewski; Agapius of Caesarea; Agathodaemon; Agathus; Helena of Constantinople;

May 22
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Aderald; Aemilius & Castus; Aghna, Luidhsech, & Caissin; Joachim de Mas y de Vedruna;

May 23
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Aaron the Illustrious;

May 24
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Afra; Aftze; Agrippina and Lauriana; Charles Wesley; John Wesley; Lanfranc; Vincent of Lerins;

May 25
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Aldhelm, Bishop of Sherborne; Bede; Pope Boniface IV; Pope Gregory VII; Madeleine Sophie Barat;

May 26
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Augustine of Canterbury; Pope Eleutherius; John Calvin; Philip Neri; Quadratus of Athens;

May 27
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Acculus; Agrius; Aquilinus; Augustine of Canterbury; Bede; Eukarius; John Charles Roper; Pope John I;

May 28
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Accidia; Acronius, Demonasia, Ammonius, & Menas; Adhemar; Aemilius, Felix, Primus, & Lucianus; Augustine of Canterbury; Germain of Paris; Lanfranc; Roberta Elizabeth Tilton;

May 30
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Ablak; Aflak; Apolo Kivebulaya; Pope Felix I; Ferdinand III of Castile; Joan of Arc; Josephine Butler;

May 31
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Agapia; Visitation (Christian) or Visit of Mary to Elizabeth;