O’Farrell or O’Ferrall, [44], [162]-[164], [331]
O’Gallagher, [58]
Ogden, Anne, [337]
O’Keenan, Teig, [39]
O’Laverty, Laughlin, [146]
Olivares, [173]
O’Mahony, Cornelius, Jesuit, [334]
O’More clan, [92]
— Roger or Rory, originator of the 1641 outbreak, [317]-[319], [347]-[349]