Surnames - The top 100 surnames in Ireland. Note: variants of the same surname are shown together with the percentage of the total. For example Kelly 97, O’Kelly 3 means that 3% of the Kelly clan use the "O" prefix and so on. 1 Murphy 2 Kelly 97, O’Kelly 3 3 Walsh 94, Walshe 6 4 O’Connor 89, Connor 9, Connors 2 5 O’Sullivan 89, Sullivan 11 6 Byrne 95, O’Byrne 5 7 O’Brien 98, Brien 2 8 Ryan 9 Smith 52, Smyth 48 10 O’Neill 92, Neill 8 11 O’Reilly 61, Reilly 39 12 M(a)cCarthy 97, Carthy 3 13 Doyle Le Connemara, Irish Eyes Are Smiling, Genealogy Chart, Genealogy Humor, Genealogy Forms, Irish Pride