O'Farrell is an anglicised form of the Old Irish patronym Ó Fearghail. According to the historian C. Thomas Cairney, the O'Farrells were part of the Conmaicne Rein tribe in Ireland who came from the Erainn tribe who were the second wave of Celts to settle in Ireland from about 500 and 100 BC.[1]
Broderick O'Farrell
- Derek O'Farrell (born 1983), Canadian rower
- Elizabeth O'Farrell (1884–1957), Irish revolutionary
- Emer O'Farrell (born 1981), Irish athlete
- Finola O'Farrell, British judge
- Francis Fergus O'Farrell, Irish soldier
- Frank O'Farrell, Irish footballer
- Henry O'Farrell, Australian assassin
- Jasper O'Farrell, American politician
- John O'Farrell (disambiguation), several people
- Josh O'Farrell, American politician
- Lauren O'Farrell (born 1977), British artist
- Luke O'Farrell (born 1990), Irish hurler
- Maggie O'Farrell, Irish-British novelist
- Maud O'Farrell Swartz (1879–1937), American politician
- Maureen O'Farrell, British actress
- Michael O'Farrell (disambiguation), several people
- Mitch O'Farrell, American politician
- Patrick O'Farrell, Australian historian
- Patrick H. O'Farrell, American biologist
- Pierre O’Farrell, American actor
- Richard O'Farrell (British Army officer) (died 1757), British colonel
- Richard O'Farrell (Irish Confederate), Irish soldier
- Séamus O'Farrell (died 1973), Irish politician
- Seánie O'Farrell (born 1977), Irish hurler
- Tadeo O'Farrell (died 1602), Irish bishop
- Talbot O'Farrell (1878–1952), English singer
- Tony O'Farrell (born 1947), Irish mathematician
- Ursula O'Farrell (née Cussen; born 1934), Irish author