1. Ó Briain, Liam, 1
2. O’Brien, Daniel, 1, 2, 3, 4, 5, 6, 7
3. O’Brien MP, Pat, 1
4. O’Brien, William (ITGWU), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16
5. O’Brien, William (United Ireland), 1
6. O’Carroll, Cllr Richard, 1, 2, 3
7. O’Brien, William Smith (Young Ireland), 1
8. O’Casey, Sean, 1, 2, 3, 4
9. O’Connell, Daniel, 1, 2
10. O’Connell (Sackville) Street, 1, 2
11. O’Connor Power, John, 1
12. O’Donovan Rossa, Jeremiah, 1, 2
13. O’Donovan Rossa, Mrs Molly, 1
14. O’Farrell, nurse Elizabeth, 1
15. O’Hanrahan, Michael, 1
16. O’Kelly, Seán T, 1
17. O’Leary, John, 1, 2
18. O’Leary, Michael, 1
19. O’Lyhane, Con, 1, 2
20. Oman, William, 1, 2
21. O’Rahilly, Michael J (The O’Rahilly), 1, 2, 3
22. O’Reilly, Mollie, 1
23. O’Shannon, Cathal, 1
24. O’Shea, Katherine, 1