| A roaring bedlam: the fair at Tullinadaly | O'Neill, Sean | Article in Journal | | 2016 |
| Mother Agatha O’Brien (1822-1854). The story of a remarkable Carlow nun | O'Neill, Seán | Article in Journal | | 1995 |
| O'Neill : people and places | O'Neill, Seán | Monograph or Collective Volume | Ballinakella | 1991 |
| The O'Neills of Leinster : an investigation into the origins of the O'Neills of Magh Da Chonn-Moyacomb - Leinster | O'Neill, Seán | Monograph or Collective Volume | Ulster Clans Centre | 1992 |
| The O'Neills of Nagh dá chonn | O'Neill, Seán | Article in Journal | | 1993 |
| The O’Neills of Magh da chonn | O'Neill, Seán | Article in Journal | | 1995 |