A
- Abbey Street Upper, Dublin, 1
- Abbeydorney, County Kerry, 1
- Active Service Units, 1, 2, 3, 4, 5
- Acts of Union, 1800, 1, 2, 3
- Adam Court, Dublin, 1
- Aherne, James, 1
- Aherne, Jeremiah, 1
- Aherne, Joseph, 1, 2
- Aherne, Leo, 1
- Aherne, Liam, 1
- Ailesbury Road, Dublin, 1
- Alexander VIII, Pope, 1
- Allen, Seán, 1, 2, 3
- American Commission on Irish Independence (ACII), 1
- Ames, Peter, 1, 2
- Amnesty Association, 1
- Amritsar, India, 1
- An tÓglach see tÓglach, An
- Analeentha, County Cork, 1
- Anderson, John, 1, 2, 3, 4
- Angliss, Henry, 1
- Anglo-American Oil Company, 1
- Anglo–Irish Treaty, 1921, 1, 2, 3;
- anti-Treatyites, 1, 2, 3;
- debates, 1;
- pro-Treatyites, 1, 2, 3, 4, 5;
- ratification, 1
- Applesby, Corporal, 1
- Arbour Hill, Dublin, 1
- Archer, Liam, 1
- Archer, Mr, 1
- Ardfert, County Kerry, 1
- Ardrahan, County Galway, 1, 2
- Army Comrades Association (Blueshirts), 1
- Arnon Street, Belfast, 1
- Asgard, the, 1
- Ashbourne, County Meath, 1, 2, 3
- Ashe, Thomas, 1, 2, 3, 4, 5, 6, 7
- Ashtown, Dublin, 1, 2, 3
- Asquith, Herbert Henry, 1, 2, 3
- Athlone, County Westmeath, 1
- Attymas, County Mayo, 1
- Aud, the, 1
- Aughrim, County Cork, 1
- Australia, 1, 2, 3
- Auxiliaries see RIC, establishment of Auxiliary Division