Aachen
Aaron
Abaddon
Abandonment
Abarca, Pedro
Abarim
Abba
Abbadie, Antoine d'
Abban Saint of New Ross, 
Abban Saint the Hermit, 
Abbé
Abbeloos, Jean Baptiste 
Abbess
Abbey
Abbo Cernuus
Abbon, Saint
Abbot
Abbot, Henry
Abbreviation, Methods of
Abbreviations, Ecclesiastical
Abbreviators
Abdera
Abdias
Abdias of Babylon
Abdication
Abdon and Sennen, Saints
Abduction
Abecedaria
Abecedarians
Abel (Son of Adam)
Abel (Biblical Location)
Abelard, Peter
Abelly, Louis
Abenakis
Aben-Ezra, Abraham-ben-Méir
Abercius, Inscription of
Abercromby, John
Abercromby, Robert  
Aberdeen, The Diocese of
Aberdeen, The University of
Aberle, Moritz von
Abgar, The Legend of
Achaicus Achaz Achéry, Lucas d'
Achiacharus
Achimaas
Achimelech
Achitopel
Achonry  
Achor Valley
Achterfeldt, Johann Heinrich
Achtermann, Theodore William
Aci-Reale, The Diocese of
Ackermann, Leopold
Acmonia  

Acolouthia
Acosta, Joaquín
Acquaviva
Act of Settlement
Acton, Charles Januarius
Acton, John
Acton, John Emerich Edward Dalberg
Acton, John Francis Edward
Acts, Canonical
Acts, Human
Acts, Indifferent
Acts of the Apostles
Acts of Roman Congregations
Actus et Potentia
Actus primus  
Actus Purus
Acuas
Ad Apostolicae Dignitatis Apicem
Ad Limina Apostolorum
Ad Sanctam Beati Petri Sedem
Ad Universalis Ecclesiae
Adalard, Saint  
Adalbert I
Adalbert, Saint  
Adalbert, Saint
Adam  
Adam in Early Christian Liturgy and Literature
Adam, The Books of
Adam of Bremen
Adam of Fulda
Adam of Murimuth
Adam of Perseigne
Adam of St. Victor
Adam of Usk
Adam, John
Adam, Nicholas
Adam Scotus (Theologian)
Adami da Bolsena, Andrea
Adamites
Adamnan, Saint  
Adams, James  
Adams, Ven. John
Adana

Adar
Adda, Ferdinando d' 
Addas
Addeus and Maris, Liturgy of
Addresses, Ecclesiastical
Adelaide, Archdiocese of
Adelaide, Saint  
Adelaide, Saint
Adelham, John Placid  
Adelmann (Bishop)
Aden
Adeodatus I, Pope Saint  
Adeodatus
Adeodatus (II), Pope Saint  
Adeste Fidelis
Adjuration
Administrator
Administrator (Of Ecclesiastical Property)
Admonitions, Canonical
Admont
Ado of Vienne, Saint
Adonai
Adonias
Adrian I, Pope (772-95)
Adrian II, Pope (867-872)
Adrian III, Pope Saint (884-885)
Adrian IV, Pope (1154-1159)
Adrian V, Pope (1276)
Adrian VI, Pope (1522-1523)

Agapetus I, Pope Saint (535-536)
Agapetus II, Pope (946-955)

Agatho, Pope Saint 
Alexander I, Pope Saint
Alexander II, Pope
Alexander III, Pope
Alexander IV, Pope
Alexander V
Alexander VI, Pope
Alexander VII, Pope
Alexander VIII, Pope