

| AIDS care-givers | Aloysius Gonzaga |
| AIDS patients | Aloysius Gonzaga, Peregrine Laziosi, Therese of Lisieux |
| Abandoned children | Ivo of Kermartin, Jerome Emiliani |
| Abbeville, France | Wulfram of Sens |
| Abdominal pains | Erasmus (Elmo) |
| Abingdon, England | Edmund Rich of Abingdon |
| Abortion, protection against | Catherine of Sweden |
| Abruzzi region of Italy | Gabriel of Our Lady of Sorrows |
| Academies, Roman Catholic | Thomas Aquinas |
| Acadians, Cajuns | Our Lady of the Assumption |
| Accountants | Matthew |
| Accused (falsely) | Raymond Nonnatus |
| Achaia | Andrew, Apostle |
| Actors | Genesius, Vitus |
| Advertisers, advertising | Bernardine of Siena |
| Advocates | Ivo of Kermartin |
| Africa, Central | The Most Pure Heart of Mary |
| Africa, North | Cyprian of Carthage |
| Africa, Southern | Mary, on feast of her Assumption |
| African Catholic Youth Action | Charles Lwanga |
| Agirone, Sicily | Philip of Agirone |
| Air crew | Our Lady of Loreto |
| Air crew, Belgian | Our Lady of Loreto |
| Air crew, French | Mary, on feast of her Assumption |
| Air crew, Spanish | Our Lady of Loreto |
| Air Force, Argentinian | Our Lady of Loreto |
| Air travelers | Joseph of Cupertino |
| Airborne (Paratroopers) | Michael the Archangel |
| Alabama | Our Lady of the Gulf |
| Alaska | Our Lady of the Kodiak and the Islands |
| Albania | Mary, Mother of Good Counsel |
| Albi, France | Cecilia |
| Alcala, Spain | Justus and Pastor |
| Alcira, Valencia, Spain | Bernard, Gracia, Mary |
| Alessandro, Italy | Trifone |
| Alexandria, Egypt | Cyril of Alexandria |
| Alexians | Alexius |
| Alezio, Italy | Our Lady of the Assumption |
| Algeria | Cyprian of Carthage |
| Alpine troops | Maurice |
| Alpinists | Bernard of Montjoux (or Menthon) |
| Altar Servers | John Berchmans |
| Amalfi, Italy | Andrew, Apostle |
| Ambassadors, Argentinian | Gabriel the Archangel |
| American Indians, Native Americans | Anthony of Padua |
| Americas | Our Lady of Guadalupe, Rose of Lima |
| Ammunition/Ordnance/Explosive workers | Erasmus (Elmo) |
| Ancona, Italy | Judas Cyriacus |
| Andalusia | John of Avila |
| Anderlecht, Belgium | Guy of Anderlecht |
| Andorran security forces | Our Lady Help of Christians |
| Anesthetists | Rene Goupil |
| Angola | The Most Pure Heart of Mary |
| Animals | Francis of Assisi, Nicholas of Tolentino |
| Animals, danger from | Vitus |
| Animals, domestic | Antony the Abbot |
| Antioch | Barnabas |
| Antwerp, Belgium | Walburga |
| Aosta, Italy | Gratus of Aosta |
| Apologists | Catherine of Alexandria, Justin Martyr, Thomas Aquinas |
| Apoplexy (Strokes) | Andrew Avellino |
| Apostleship of Prayer | Francis Xavier |
| Apothecaries | Cosmas and Damian |
| Apprentices | John Bosco |
| Aquila, Italy | Maximus of Aquila |
| Arabia | Our Lady of Arabia |
| Aragon, Spain | Agathoclia, Braulio, George |
| Archaeologists | Damasus |
| Archdiocese of Saint Louis, Missouri | Louis IX |
| Archdiocese of San Francisco, California | Francis of Assisi |
| Archdiocese of Tuam, Ireland | Jarlath |
| Archers | Sebastian |
| Architects | Barbara, Thomas, Apostle |
| Architects, Italian | Benedict, Abbot |
| Architects, Spanish | Our Lady of Bethlehem |
| Argentina | Our Lady of Lujan |
| Argentinian Military Chaplains | Our Lady of Lujan |
| Arizona | Our Lady of the Highways |
| Arkansas | Our Lady of the Holy Souls |
| Armenia | Bartholomew, Gregory the Illuminator |
| Armies | Maurice |
| Arms dealers | Adrian of Nicomedia |
| Army of the Andes | Our Lady of Mt. Carmel |
| Army, Argentinian | Our Lady of Mercy |
| Army, Ecuadorian | Our Lady of Mercy |
| Art | Catherine of Bologna |
| Artillery | Barbara |
| Artists | Luke, Catherine of Bologna, Bl (Fra) Angelico |
| Artois region | Isberga |
| Ascoli Piceno, Italy | Emidius |
| Asia Minor | John the Apostle |
| Assisi, Italy | Francis of Assisi |
| Astronauts | Joseph of Cupertino |
| Astronomers | Dominic |
| Asylums (for the mentally ill) | Dymphna |
| Athletes | Sebastian |
| Augsburg | Afra, Ulric |
| Australia | Our Lady Help of Christians |
| Australian Military Chaplains | Our Lady Help of Christians |
| Austria | Joseph, Maurice, Coloman, Leopold, Florian |
| Authority, persons in | Ferdinand III of Castile |
| Authors | Francis de Sales |
| Avenay, Champagne, France | Tressan of Mareuil |
| Aviators, aviation | Our Lady of Loreto, Therese of Lisieux, Joseph of Cupertino |
| Avignon | Agricola of Avignon, Benezet |
| Aynac, France | Genistus |
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